Does introducing new partner to ex make co-parenting easier or harder?

My ex met my girlfriend briefly at a school pickup last month (she was just there, wasn't weird) and suddenly ex's attitude shifted. She's been way more flexible about schedule swaps, actually uses the co-parenting app, even made a joke yesterday.

Is she just being nice because she sees I'm "settled down"? Or is she relaxing because she's not worried I'm spiraling? Either way it's made things SO much easier but I feel weird about it. Like... did I need to find someone for her to respect me as a co-parent? That's messed up.