Your feelings are your feelings. Personally, I'd feel sad that I didn't have a better relationship with her, but not guilty for being happy to spend your Thanksgiving with someone you enjoy more. I hope you are able to let go of this part of things and have a great holiday!
My grandparents have all passed away now and I wish I would of spent more time with them !
Just enjoy the day. You don't have to like your relatives but sometimes you have to spend the holidays with them! Yikes.<br />
Just remember to give Grandma another chance at some point in the future. Sometimes you see people differently at different times in life. It won't hurt to try.
I'd give anything to have one more Thanksgiving with either of my grandmothers, yes I too liked one more than the other but did not hate either. Everyone's situation is different, but one day she will be gone and you might regret not spending time with her.