My daughter went through a similar phase at that age. She still hasn't fully snapped out if it.

But I find that continuing to offer different activities helped. Eventually I found something she liked to do.

Could it be that maybe she is just too busy during the week that she just wants to do nothing with you?

And I say it's incredibly kind and generous to even think about buying flowers for your ex. I think it says a lot about the kind of person you are :)