The whole "Paying thing" really only applies when you FIRST meet a girl.
NEVER offer to buy drinks when you haven't talked to her yet.
NEVER send flowers or candy when you've never spent any time with her.
However: When you've talked to her a bit & have some interaction together, then it's NOT WRONG to pay for stuff. Especially if you ask her out.
When she has invested time & interest in you, it's totally OK to pay for things.
That's why she got edgy.
Guys take ths whole "don't pay" thing waaaaaay out of context & it blows up on them... and that's why.