So what you're saying is, you want to drug her so you can have some sexy time rather than wait till she's comfortable getting sexual. I don't know about you, but to me it sounds like you don't really give a damn about your girlfriend's feelings.
Any sane, honest person in a relationship will take into consideration their partner's opinions and feelings.
Wait till she's comfortable. Don't force her into it or guilt trip her. Don't you dare.
If neither of you are happy, call it off.