This is a grammar thing.
Is the sentence “I proposed to my fiancee.” correct, or would it be “I proposed to my girlfriend.”
Time agreement or something IIRC, clarification please?
IANAExpert on this or anything, but I would think “I proposed to my girlfriend.” is correct.
I asked myself, “Why would someone propose to his fiancee?”
In the same way that you don’t toast toast, you don’t propose to your fiancee.
Maybe the fiancee won’t set a date? 
I’m pretty sure the latter is correct.
Although the former could possibly be correct also, maybe you asked the question again just to make sure. 
I would just say “I proposed.” If you have a girlfriend (or fiancee), who else would you propose to. “I proposed to my girlfriend” seems redundant.
They are both grammatically correct. There is just a slight logic problem with “I proposed to my fiancee.”-why would you propose to someone already designated to become your wife? Peculiar but not impossible.
This is really a matter of making sure your referents are clear-‘I proposed to my fiancee’ is better than ‘I proposed to my girlfriend’, because someone could respond to the latter, ‘Which girlfriend? You’ve had more than one, right?’. ‘I proposed to my fiance’ is shorthand for the cumbersome ‘I proposed to the woman who is now my fiance’. You’re using ‘my fiance’ as a definite descriptor (on the theory that you have only one fiance-you do, right? ), not as a time-dependent indefinite descriptor.
This is an accepted method of communication. People often will tell stories about, say, how they met their spouse, or when they saw an older model of their car, and so forth, and I don’t think anyone gets confused. (Wait a minute-you married your spouse before you first met?!)
“I proposed to my fiancee” sounded weird, but then I realized that “I proposed to my wife” sounds normal, even though it should make even less sense. So, who knows?
It could depend on your meaning of “proposed”, you could propose to your fiance that you move out of your apartment.
To be extra clear, it should be: “I proposed to my girlfriend and my fiancee accepted”.
It’s not ungrammatical, merely a rhetorical device called “prolepsis.” Another example: “I first saw the dead man when he stepped into the street and just before he was hit by the truck.” No one is likely to make the mistake of assuming the man stepped into the street after he had died.
Or you could say, “I met my wife in college.” Of course in college, she wasn’t your wife. That happened later.