I recently re-watched season 1 and have never been a huge Katherine fan, but seeing how far she has come from that girl and the effort she is now making is positive.
Seeing Ashley trying to latch on to Thomas by spouting things she has no business saying and doesn't actually know anything about is disgusting. I had to stop watching. She can support Thomas without resorting to that. She's been in those kids' lives a year and knows nothing about the custody arrangement.
I don't think anyone is calling Katherine a saint but Ashley doesn't even have common decency. Those women were pleasant to her on the trip. Katherine had a pleasant lunch with her, But one birthday party Katherine thought would be awkward (after she declined a Halloween invite as too soon) and Ashley went off the rails.