Maybe would be wise to talk to her about her past..... something bad could have happened in the past with her.... and that why she is behaving like that..... (and please be sober when you do it)
Dude I have found that as soon as you get the Ok to be rubbing her through the pants, I just slip my hand down her pants and continue on. If they will let you rub them fully outside but not in... Well then your guess is as good as anyone else's.
^^It's alright guys I'm not stressing over this. She already agreed to hang out again. It'll happen next time.