Well, since she was already dating the other guy when you two got together, that's 4 good months you wouldn't have had with her if it weren't for poly. Just another way to think of it.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.