Should I tell her how I feel or just walk away?

I've known this girl for about 3 years, we used to talk only occasionally and now are talking and hanging out about once a week. She's really hard to read and I'm not sure if she's "testing the waters" or just friendly. Here's the timeline:

I've called her to come hang out with my friends at our house several times the last few weeks and she always says yes, but doesn't usually stay more than an hour. We talked about going out for drinks a few weeks ago, just us and planned it two weeks in advance. Half an hour after she was supposed to have been at the bar I texted her and wanted to make sure we were still on, and she said she was home and was just going to hang out there. So she stood me up. The next day she texts and apologizes for it and asked me to go out to the bar that night (with her friends). Its common knowledge that being the only guy out with several girls is, in all practicality, a chick. I declined, in no small part to not wanting to be her b**ch. Afterwards she came over to hang out. Last night I'm going out with my friends to the bar, I call her and ask if she wanted to join me, she did and met us at the bar. After a few minutes she and I broke away and sat at the bar (we were 2 of 10 people in the joint so it was quiet and somewhat private) and talked for over an hour. She mentioned things that we should do together (baseball games, museums, etc) and said she wanted to spend new years with me and wanted to hang out what was today. When she got home she texted me thanking me for a great evening and said she enjoyed my company.

Looking at it from a logical standpoint, I have no real evidence that she has any feelings towards me and a lot of circumstantial evidence that she doesn't. But little things like looks and things make me wonder.

There really is no risk of telling her how I feel, with the exception of rejection, which, if I wanted to feel that bad there are more dignified ways of accomplishing it. But at the same time, I don't want to waste my time and kill a great friendship with one of the few women I actually respect (it's earned, ladies) and enjoy hanging out with.

The question then is, should I tell her, or should I forget about it?