That’s how I feel, not what I recommend for you.
I’d help her if she asked.
But no on anything really bad she was doing for a thrill.
What if she does it for business reasons?
Compare the replies in the two threads. I wonder if any of the kneecaps would turn them in?
I personally believe that sometimes, crime is justified–including some thefts, vandalism, and even some murders. There are other things that’re considered ‘crimes’ that I have no issue with, such as urinating on the grass or on a tree in public.
If my SO committed a ‘crime’ which falls into either of the aforementioned categories, I would keep my lips zipped. This goes for friends, too, as well as anyone (except people I wish to get back at–they’ll get reported in a heartbeat just for the sake of getting them in trouble).
An example of such a crime: a friend of mine and I confronted a guy that had, basically, taken my love and shat all over it during the dating process. After we left the guy’s apartment, I was in the lead, with my friend behind me, when I hear a “scrrrrrrrrrrrrrrrrrrrr-ii-ii-ii-itch!” behind me.
I turn around; my homie left a nice, deep scratch down the side of the guy’s car.
Lips: zipped. Laughs: plenty. 
I’m sorry your heart was broken but not sure that justifies vandalism.
No I wouldn’t turn them in for anything other than child rape/harm. In that case I would leave first, and then call the cops.
Violence, physical or sexual, to myself or a child.
That’s pretty much it.
WTF is wrong with you?!? OK-----Dont’t fight the hypothetical. You are asking me to imagine that my partner has betrayed me.
If it turns out that I do not know my partner well enough to know that his beliefs are so antithetical to my beliefs that he acts counter to my being; then yes, I would turn him in. Because when I parse your question, “crime” is really a code word for “something really bad”----which is pretty generic by itself.
Of course I wouldn’t turn my significant other in for a crime. Do you know why? He wouldn’t commit a crime that would offend me—at least not on purpose without purpose. That’s one of the reasons why he’s my significant other. Your question is really a question of, “How much faith do you you have in your judgement of character?” I do the best I can. Is it 100%? No.
But my partner and I have managed to maintain a 19 year commitment in a hostile environment. That is, we are getting married in January, after having obtained the right to marry only this past summer.
Why are we waiting until the new year to marry? Because neither of us ever figured that two gay men could marry in south Alabama in our lifetimes and our taxes would be significantly greater if we married this year.
Taxes are necessary to maintain our society. I do my best to vote for the tax that imposes the greatest public good. Though I am supposed to pay the taxes I owe, I am also supposed to search for the greatest discount I’m allowed.
I can’t resolve the difference between personal benefit and public well-being. That’s why I drink.
If it was significant enough, I’d perhaps encourage him to turn himself in. But if it was a crime that would cause him to be incarcerated, I probably wouldn’t turn him in. Of courses, that assumes he is the same guy that I know and love today.
If he suddenly developed a heroin addiction, I might rethink that.