Okay, I apologize for what is probably too much information:

Two nights ago I was out at a bar with a group of friends, when one of their friends comes in to see us. I've met her before and she seems to be interested in me. That night though she is REALLY into me, facing me fully, playing with her hair, legs touching, letting her hand rest on my thigh, leaning into me, putting my arm around her shoulders, basically touching me every time she gets. My friends in the group kind of just let us have our own conversation for most of the night, since they could see it was on. She asks me for my number.

Yesterday after work I text her: "So I'm clocking out at work and thinking of getting some lunch. You hungry? I'd love the company"

She says sure. Can I pick her up.

We go to lunch, it's great; not a lull in conversation at all. Afterwards, I suggest doing something else, but since this was kind of spontaneous, I didnt have an idea yet. She suggests a movie (which I took as an ioi)

Here's the awkward part. Last night she was super into kino and everything, so when I realize she had put the arm between the movie seats up (so nothing is between us), I do the typical arm around the shoulder thing, which she seemed to like the night before.
She lets me, but she seems 'stiff'. So after a bit I take my arm away, and let more of the movie go by. Later on, I try again, and she shakes her head no. I made the AFC mistake of asking why. I meant it jokingly, but I don't think it came off that way.

(I realize as I'm typing this that it seems like a stupid little thing, and maybe it was my own perception of it being awkward than anything, but I'm curious about how much of a fail that was. Looking for confirmation/opinions)

Movie ends. She likes it, but there seems to now be lulls in the conversation even when I try to save them. I cut my losses and drop her off because she has things she needs to get done.

She texts me after dropping her off though "My roommate is using the washer! :-/"
Me: "Haha! Aw, I guess that means paper writing time huh?"
Her:"...I was just going to watch the bing bang theory...lol"
Me: "Nice!! That gets a high five!"

So she's still texting me, which is nice. Also, later that night I picked her up again (10pmish) to go to a friend's kickback. Still, the kino and a lot of the chemistry we had seems to have disappeared and I'm not sure if I'm in friends zone instead now.

So she will be gone for a week for spring break, and I'm currently debating on whether I should try to flirt a lot in texts or be quite for a few days so try and hit the reset button on the awkward date meter.

Also: I have another girl that might come out with my tonight to see a game. Should I let the first girl know about this other girl and try to get a jealousy thing going, or is that too risky? I'd prefer to be with the first girl, so I'd rather not backfire it.

Opinions? Was the date a mess up/Do I keep texting her/do I let the girl know I have the other option and went on a date with her?