There's a story line between Violet & Cooper - they're best friends, have been forever.
Pete & Violet are married
Cooper & Charlotte are getting married
Violet & Pete spend a LOT of time together - have keys to each others' houses, go to each other whenever they're having problems, spend a lot of time on the phone with each other.
So at the end of last night's episode -they're working out a schedule of when they can hang out that doesn't interfere with their primary relationships - they had been each other's *primary* for so long - that the adjustment was difficult.
W and I looked at each other and said "Wow! Poly on tv!" but they weren't calling it that... but it was really interesting to watch the dynamics