I am frustrated with the fact that we can not seem to come to a consistent co-parenting relationship here. She seems to want to pop in and out whenever she feels like being mommy and then leave whenever she has something to do.
By "pop in" do you mean come into the house, etc? I think so that things are more realistic, it should be made more clear that she has her place and you have yours. Do you stroll into her place? I think it would help for her to get the message that you aren't in a holding pattern waiting for her to get off the snide.
You cannot be lonely if you like the person you're alone with. Dr. Wayne Dyer