Fourthwalling; Go ahead. Cinderella is very well known and old story, so if it makes sense for your character to know it, then they know it. o/ Same goes for the Disney's movie.
Threadjacking; If it makes sense, then fine by me.
Back threading; I will never say no to this. I do it all the time.
Mind-reading; Just inform me first and it should be okay.
Violence; Mental? gogogogo, she's used to that shit already. Physical..... :(
Death; lolno.
Love; I'm taking her from the point where she has just came back from the royal ball after the clock struck twelve. So she has met her Prince Charming but doesn't know who he is and hasn't married him yet.  Which means that she's available!--- However she is completely in love with that mysterious man she met earlier, so it would take a lot of time for her to fall for anyone else.
Sex; NO SEX BEFORE MARRIAGE. :(