I had so much hope and excitement for a new connection

I have been getting to know this girl during this semester, and things picked up with more conversation and my interest in her grew a lot. We are in the same club at school and one day she offered people to come visit her at work. She didn't specify who but pointed in my general area with 2 others nearby. After a day or two I took that to be serious so I decided not to waste anymore time. We have about an 8 year gap but at my age I know I would be very lucky if I could find someone even within 5 years my age since most people are married. 
So I think I spent about 2 weeks getting to know her even more 1 on 1. She seemed like she could handle my focus and attention so I didn't worry. I know for a fact she is single as well.

One day she comes to the club meeting and just dodges me. She doesn't say hello and talks to other people and sat away from me, she only asked 1 question from me that whole day (all of this is not normal). So I am a bit upset about this, I went home and struggled to be relaxed because I just got rejected again. I decided that whatever happened can't happen again, so I went straight to wall and bunker building.

There's some signs indicating maybe she's messing with me, because after getting dodged she walks by my study area on another day and waves to the people in the room but no one noticed except me. So I looked up and hesitated but eventually waved back. When people do those kinds of things it usually means they want my attention but won't give me all of what i'm looking for. She also walked away looking as if she regretted waiting for someone to notice her.

Anyway this is the pattern, and now it's been a week or two since and yesterday she was in my study group/room and immediately started saying hi and stuff. But I am so defensive now at this point I respond with very little and turn the conversation off. She got the hint and turned back to her work, but I don't even know what to do now. 

For me getting ignored like this is now a major flaw I see that I don't think is recoverable on her part (this also has a lot to do with not having the energy to accept this from a girl I like anymore). However, I still have to work with her in the club so I don't want to be petty and a cry baby but I felt a bit justified killing the conversation so far. Things aren't really awkward but I want to be able to stop thinking about her because it might be too stressful to continue trying to understand her.

I've been single for over 20 years and another event like this has me really burnt out on girls, or just trying in general.