This girl hasn't really been giving much in terms of IoI's (at least nothing I've really been able to notice/recognize.) The only slight sign of interest is her calling me to get directions somewhere, then sending me a text the next day to thank me for helping her out. They weren't even good directions!

But I was getting together with some friends to go barhopping yesterday, so I figured I'd invite her out and see if I can game her a little better than I've managed to in the past.

She had something to do earlier in the evening, but said she might come out after. Got a text from her at one point saying she was going to "pass on tonight.'

Ok, so either she really was just tired and didn't feel like going out OR she just didn't want to get together with me.

I'm going to assume the former, but then what is my next step? Am I showing too much interest if I invite her out again next week? Or maybe I could see if she wants to get lunch one day? (We work pretty close to each other...)

i been there b4, your gonna fall into the dependable friend status =(
askin me for directions when dam well shes probably goin somewhere to meetup with some other people.
try to not answer for a while, to make it appear that you been busy yourself...
of course tho i feel like alot can happen in a week like another guy entering the picture and sweepin her up .

Actually she was on her way to meet up with _me_ and some other people...

Well, I like the idea of punishing behaviour I don't like. I would not invite her again to do anything. Try to keep in touch once in a while and wait untill she contacts you for another favour. Whatever favour she asks you, never help her anymore. She needs to get punished to have said 'no' to your invitation. E.g. if she asks you directions again in a text message, don't react immediately. Make her wait many hours. She will feel really bad because she will feel rejected because she thinks you are ignoring her. Then suddenly out of the blue you respond "I don't know.". A very short but cold reply. That's it. She will feel a bit better about it but not too good because you were so cold to her. And she can't really hate you because you did reply. After several of these cold messages to her, ask her out again but not as a date. Take her out to an happening where you are gonna be with your friends and she with her friends. Then game her properly.