So I've invited a woman to a night long event and there is a ticket cost of $50 for admission. She has said she wants to go, and I told my friends I would let her know of the cost beforehand, expecting her to pay. My friends have chastised me, saying that I should pay the admission price for her.

I have no relationship with this woman aside from the fact that I used to work with her. We flirted a few times at work, but aside from that, nothing has happened at all. Do you think I'm in the wrong here or what? Let me know if you need any further details or if you think I have my head up my ass.