Any reasonably smart girl will see right through what you're trying to do. I've heard of magicians trying to use their stuff to pick up girls and never heard of a success story. Think of it this way, if you present an effect to her, she'll think "oh, that's cool", then if you somehow work it into asking for her number, you're already done. She'll most likely be thinking "sure he's good at magic, but that doesn't make me want to date him". If you've got the looks/charm it might work, but not because of the mentalism.
I'd steer clear of this idea if I were you, but there's nothing I can say to make you not do it, your mind is set.
my point exactly, a girl won't like you because of magic she'll only like you if she likes you.
Who says you can't show your charm and personality through Mentalism? Your meant to show your charm as a mentalist, a mentalist without charm is boring and dull (Search Youtube). Be human, you don't just go up and perform a trick to them and that's it, you still gotta interact with them like any of your friends. Be causal, don't use some unnatural prop like esp cards, playing cards, some prop box, etc.
Exactly the opposite has happened to me. Introduced myself to the girl; had a yarn (keep myself a tad mysterious); did some mentalism; got her number (acquired it in a subtle manner not direct); I then left the bar with my friends; she called the next day and we hooked up.
This doesn't happen all the time of course.