I'm not going to visit my mom while she's in town. I just don't want to do it.
That's pretty harsh. Why would you want to avoid her?
I just feel like avoiding her for a while.
I understand you might want some alone time, but you shouldn't completely avoid a parent.  Maybe just have a lunch together or something?  No big time commitment then.
I'm going to hang with my friends. She knows I have a life.
It won't take much time to stop and just visit for a little while. If you don't see her often she will like seeing you again.