Were you interested in possibly dating others at some point, or were you set on her being your only partner? If the former, I think her decision was unfair and premature. If the latter, maybe it really was for the best, if being co-primary with her husband wasn't considered a possible option down the line. Either way, I feel for you, it sucks to be told you're being broken up with for your own good. In addition to the normal hurt, you end up feeling condescended to.
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.