I'm sorry, Shy.
Can she articulate better for you what's going on and why she needs to withdraw? Can she give you any sort of guess at a timeline? Leaving someone hanging like that isn't so cool...
Have either of them had a poly relationship before or was this their first real try? Sometimes the feelings this all brings up can really surprise people.
Try to keep from pining away, go out and do things, do your best to actually give her her space once she feel like you've gotten the best understanding she can give you of what's really going on.
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.