It sounds to me like your Mom is very lonely, and she's trying to start a discussion - ANY discussion - just to have someone to talk to! With your Dad's work taking up ALL of his time, and the two of you girls living hours away, it looks like she doesn't have anyone to talk to. I'm glad you gave her sources of support to reach out to -- if she doesn't use them, that's HER fault, not yours. You are NOT your parents' keepers. So there's nothing you can do about it after you leave.
I hope she will reach out for support, but if she doesn't it's no one else's fault but her own. I'm VERY happy to hear that YOU are in therapy. So many of us from dysfunctional families need the help of therapy, and it sure did ME a world of good.

I spent most of my adult life in therapy, but I guess I've "graduated" because I've been told I don't need it anymore -- at least not right now. LOL
I wish you the very best. God bless and please take care of YOU. Happy New year!! Hugs, Lee