Girl rejected me twice... I can't get over her...?

[Thisguy]

So I am a 17 year old boy and this wonderful girl entered my life and she was considering dating me but she rejected me and then my feelings never subsided and about 5 months later, I basically told her that I'd like a second chance and she turned me down again. and even now probably a month after that, I find myself unable to not think about her constantly.
I've started to completely avoid her in person though. we have a school activity where we see each other on every few weekends. But I avoid her cuz I don't wanna like her... But I do...And the last 2 times I've seen her over the weekend, she's texted me like twice telling me that I should come sit and talk with her and our other friends.I usually just make up some excuse and don't go
Us and our other friends have a 6 person group chat on Facebook where I talk to her a lot. And we text each other every now and again. It's usually her starting the conversations, though. I'm not sure if I should continue to avoid her or what, though