So sorry to hear that.
It always blows my mind that people think it's even possible to have regular sex with someone without having to worry that emotions might develop. There are actually chemical reasons that the two are linked (oxytocin released after sex, etc), you literally can't help how your feel. It's your actions that you can control, and your actions have been 100% honorable in that you talked to your partner about it rather than acting rashly.
Having her come here might help, as NYC suggests? Or maybe she does just need time and space.
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.