Do I move forward or back off?

Ok so there's this girl at work who I've been doing a favor for. ( She was saying she couldnt find a coke bottle with her name on it. So when I find one I get it for her. Im a wuss. I know.). Anyway one day I jokingly ask what Im getting out of this and she says she will get me a sub. I said ok. After a week or so we went on her lunch and it was a bit awkward. She was very flirty when we were alone then when other people were around she began to lock down. She apollogized later saying she was having a long week. here's my question. I kept buying the drinks for her. But I said I was going to stop buying them. And she told me that she liked getting them. Also she is very flirty when we are alone. Am I missing something? If she isn't interested wouldn't she want me to stop? Im a bit lost here.

Would she want you to stop buying her things if she's not interested? Well, a decent girl who wasn't interested would be returning favours to you so that she wasn't in your debt or misleading you. But a girl who will take advantage will love having stuff bought for her and have no regard to how you feel.

That being said, I'm wondering why you *told* her that you'd stop buying things for her. Why didn't you simply stop doing it without mentioning it? It must have been a very awkward discussion.