You may well be right that there are no poly-geeky girls in Danville, but I promise you there are in NoVa, DC, and Baltimore. Heck of a lot closer than OH.
You have no more reason to feel guilty than she does for the distance, you both knew the score going into it. As for her desire to be mono, that is her business and hopefully she will sort it out. It's not your fault, you've been very clear about your situation.
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.