Being Unkind

Being mean to someone is more work than you would think.
It's not something I normally do, so maybe I'm just out of practice.
Here's the story, this summer, Spencer and some of his friends got in trouble. His friend Danny didn't have any consequences for the actions and the mother told me she had encouraged Danny to be a better influence on Spencer, which made me crazy, because he was doing the same things that Spencer was, but he lied to his mom about it.
So this summer, when the mom came up to me and put her arm around me, I said that I couldn't talk to her then. I was still mad that she fell for Danny's BS.
What I discovered through the summer and fall, was that it is kind of nice to not be talking to this mother. She has ADD and talks incessantly. She gossips about all the kids in the high school and she doesn't understand limits. I'm constantly having to say, "You're in my space" when she moves in too close, or "We were in the middle of a conversation" when she walks up and starts talking. So that can get kind of tiring.
The mother of another boy and I had planned to ride to a basketball game together Friday night. I got a message from Danny's mom saying "Can I ride with you to the game?"
We were leaving in about 20 minutes and I had looked forward to spending time with the other mother. I simply ignored the text.
Well, about half an hour into the game, Danny's mom arrived and sat by us.
The other mother isn't as good about setting limits. She had even complained that Danny's mom had ridden with her to most of the soccer games and she tried to leave town early to avoid her, but she couldn't bring herself to say no.
At one point, the other mother and I were talking about her brother who is going to New York for Thanksgiving when Danny's mom jumped in: "Now who was this? What was happening?" Aaargh. See how annoying that is?
So I left without having made eye contact or talking to Danny's mom.
I don't think I can keep it up through the whole basketball season though.
So what should I do? Simply accept the fact that she's going to glom onto us throughout the season and put up with it.
Lay out some boundaries, like "you can ride with us to every other away game but not every time."
Point out that she is very annoying the way she talks constantly and interrupts people?
My running friends said I was being too harsh, but she really doesn't get boundaries unless they are clearly stated.