True especially since Marceline is a perpetual emo crybaby and PB is still an emotionally and psychologically manipulative despot. It works out better that PB and Marcy are together since PB never cared for Finn. He’s just another tool for her to use, abuse, and dump when she gets bored. PB knows Finn will die so she played on his emotions to control him until she saw no use in him. Then she moved to Marcy since unless someone Stakes or Sunrises her ass. Marcy’s the perfect tool because she’s completely ruled by her emotions, even more so than Finn. Plus since she’s crippled all the competition, the only person who was a threat was Marcy. So lezzing out and pussy-whipping the only threat makes her look good optically and makes sure Marcy is always eating out of her hand like how she trained Finn to be her lapdog.>TL;DR
It doesn’t matter because PB is just gay for a power play and if Marcy outlives her usefulness she’ll toss her away like she did with Goliad, Rattleballs, or any of her other experiments/tools she got bored with.