First of all I just wanna say about her idea of a movie date, not all that bad an idea, read up on Chief's sticky about movie dates (top of this section) a lot of good points in there which I used on a date last week (and will be again on friday

).
With regards to buying drinks you can go a few different ways with this, you can either come out and say "I'll get the first round, you get the next one", you can turn it into a game "Let's play rock paper scissors, losers buys the first round!", or you can do a little test to see what kind of girl she is, don't mention anything (for the first round) just ask her what drink she wants, get it for her, eventually after the two of you have finished your first drink, she's gonna want another, here don't do anything for like 20-30minutes and just see if she actually gets up and offers to buy you one. I take that scenario as a massive IOI, as now she isn't just investing time in you, but money aswell. You may get a bit thirsty during this time, here's another good reason to have chewing gum handy, it can moisten your mouth a bit when you haven't got a drink there as well as make your breath fresh for kissing (no-one likes bad breath).
Personally I normally take the third option and if it doesn't play out if she says "lets get another drink" or whatever I take that as a cue that she wants me to buy her one (otherwise she'd just go get herself one right?). I'll just fall back on one of the other two with a slight change of phrase like "Hey I got the first round, it's your turn" or a classic bit of Tommy Cooper (for those who aren't from UK he's a legendary comedian) where you say "What are you having?" she'll say what she wants, then you say "Great, I'll have the same thanks" it's a nice cocky/funny one.