This is just so hard to read. You say Piper will not stay with Colada if she doesn't accept you and over and over again, their actions scream (to me anyway) that they at both doing things to push you so far you will walk away, giving Colada exactly what she wants, your husband without you. All the entertaining in YOUR house, interacting with YOUR kids, while you are supposed to vanish into the woodwork and become invisible is so incredibly dissrespectful it boarders on abuse. If she can't even deal with your existence, then she needs to get he FUCK out of your home and stay out until she is willing to be respectful of you.
I get the need for space and trying to find a compromise when things aren't working, but that doesn't mean you need to be a doormat while this women walks all over you and invades your home. If they want to play at pretending you don't exist, they should do it someplace your kids won't have to witness it. This whole situation is a massive train wreck in the making.