This is just sneak bragging about how you look good in any hairstyle, isn’t it? 
To borrow the line from the old western “No brag, just fact”
OK, I’m not going to call you a scumbag because others have done the same, instead I have just a couple points to make.
First, you have now learned that long hair is more important to the package than you thought it was. (I’m assuming you didn’t already know that).
Second, if you intend to stay with this lady then you need to level with her, but do so in positive terms. Tell her that you really do prefer the way her hair was over how it now is. That doesn’t mean you no longer find her attractive at all, just that you preferred the old hair. Reassure her that the final decision is hers, but if she cared to know your preference you’d rather she grow it out again. Like I said, keep it positive but be honest (yes, I know sometimes that’s hard to do simultaneously).
It’s worth mentioning that there is in a difference in early relationships and long term one. Long term any guy knows he’ll see his wife wear a lot of different hair styles and clothing. It kind of goes with having a woman for a spouse. 
Short term – IIRC people try to make the best impression on dates. They spend more time grooming and selecting clothes. Whatever attracted you to the person may be superficial but it did catch your eye. There’s a reason male birds have bright colored feathers. Visual attraction is important early in the relationship.
If a girl I had dated for a short while drastically changed their appearance it would make me wonder what was going on. Especially if the girl knew I was strongly attracted to her prior appearance. It’s like do you even care it I’m attracted to you anymore? Is she trying to tell me that she doesn’t care if I’m still interested in her? Maybe this is her way of gently breaking off the relationship. It’s been decades since I dated but I still remember those insecurities that goes with an early relationship.
YMMV
At least you noticed the change. I might not have.
Well, I guess I’m on board – some girls can rock the short hair and some can’t.
She probably wasn’t a real serious girl or else she would have asked your opinion, right? So, now you know she didn’t really think of you in “that way” – probably a pretty fly way to tell you to eff off, on her part.
ETA or at least her way of telling you she wasn’t your “girlfriend,” whatever you think that means. Face it, she’s not and never was your girlfriend – if she was, you wouldn’t be asking this complaint.
She’s my gf. She’s even brought up marriage and many other things.
Anyways I’ve done some more prodding and although she likes the haircut she said it was a bit too short. It was done for a donation to Locks of Love. Seems like she’s done that before. She’s not gonna continue with the style though. She’s gonna let it grow out.
Broomstick had it right when he/she said I have learned that her hair is a much more important part of the package than I thought it’d ever be.
she made a sacrifice to help others which you both should value.
maybe next time she could grow it terminally long (where it doesn’t grow any longer, maybe 3 or more years). then get it cut half length, resulting in still a long hair style and still a donation.
Next time, make sure she donates pubic hair only.
And supportive when I donate to really cool charities.
Yup, Mr. Gracer is getting a hug just for caring about me, rather than my hair.
I think that’s awesome. Good on her. Hair grows and you will get used to it. Its very possible that your dislike for the look is because its unfamiliar.
I was once in a relationship with a man who had a beard. I loved his beard, it was part of him. One day, he got a new job and had to shave his beard. The next morning, I woke up to this clean shaven guy in my bed and during that moment between sleep and awake, I freaked out. It was kinda like “OMG, what did I do last night and who is this and wait, I wasn’t drinking last night…”
You’re considering marriage and it never came up that she was cutting her hair for charity? It didn’t even come up when you got unreasonably upset about it? Good for her, though, for doing it despite your significant distaste.
See, I don’t get this. She wants to cut her hair (to donate as it turns out, but the reason why is fairly immaterial). What is there to ‘run by’? And why the need to ‘run by’. I mean, she just wants to cut her hair. Why does that need to be ‘run by’ someone else? And how is that showing consideration? I’m baffled here. I’ve never understood ‘running something by’ someone, if I was intending to do it anyway. I guess, there’s a very small chance the other person may suggest something that she hadn’t considered… but it’s just a haircut. Can you explain what the outcome, or purpose of running it by your partner is, because I’m seriously baffled that this is an expectation by some people
I’m another person who has had long hair almost all my life and while I’ll get a trim to even out the bottom/remove split ends without consulting my mate of 25 years I wouldn’t make a drastic change without at least a little warning. Yes, it’s my hair and I can wear it however I want or even shave it all off, but it’s shocking to make such a drastic change and appearances are part of who we are.
As for Locks of Love - I’ve been donating to them for the better part of a decade now. I usually grow my hair at least waist length, then cut it to fall slightly below my shoulders. That gives them enough for my purposes, and I’m left with enough that my appearance isn’t radically altered from long hair to short.
As for the OP - if both of you agree the new hairstyle isn’t that great well, you both learned something, and that’s not all bad. Meanwhile, if you continue the relationship, try to concentrate on the other bits of her you enjoy and appreciate while her hair grows out.
What?
While I certainly take into consideration my partner’s preference for my appearance, ultimately, it’s my appearance. If I get my hair cut or dye it a different color, it’s not a sign that I’m about to dump you. This all smacks of how all the Duggar girls wear their hair long and permed just how daddy likes it. Gross.
Amen.
Meh. I will certainly offer advice if asked (a lot of straight guys will outright ask if they see you as someone who is stylish) or I will give my opinion (“I’d really prefer if you didn’t grow a full beard and put beads in it Captain Jack Sparrow style, Stephen**”), but ultimately it’s their choice. I liked my ex better when he had a goatee because it made him look a little bit older and more dignified-- something I openly told him-- but I certainly didn’t dump him when he’d go clean shaven.
Because ultimately? Jesus Christ, it’s just hair.
**that’s a real direct quote I had to utter to a boyfriend once.
What? She doesn’t love him unless she keeps her appearance just the way he likes it?
Because appearance is a pretty big deal no matter how shocked people want to act when someone actually admits it. If your partner one day is going to wake up looking like someone you would not date entirely by their choice then you have every right to be upset. Cutting off all your hair drastically alters your appearance, I have never dated a woman with short hair because i do not find it appealing at all.
I’m so happy I cut my hair off while not in a relationship. This way, all the guys can know that I’m the kind of girl who sometimes chops off all her hair (much shorter than the bottom of my neck), and won’t have to feel all betrayed if it happens again.
While it’s a big deal initially, there’s a point in a relationship where, I hope, one’s desire to be around the other is much less physical than it once was. In a relationship where one is considering marriage, you have to think “will I still love this person through the soft and the hard,” so to speak. If a guy still looks at his partner and thinks “I don’t want to be with you if I’m no longer physically attracted to you,” then the relationship’s lasting potential is limited.
She cut her hair off to donate to charity, and instead of telling her how awesome that gesture was, all you can do is whine that you don’t like the way she looks now. Way to go, dude, it’s all about you.