So, update.
She was unable to pass the egg in the end, and we had to send her in for surgery. Thankfully, she survived (and was spayed at the same time, one- to prevent this from ever happening again, and two/ to stop her injured reproductive system from causing further harm). She's recovering now and is doing well, if not quite tired. Poor little thing, has to wear a thick cone which totally throws off her balance. And she has to be kept in a tiny cage so that she doesn't hurt herself, which is bad enough for her.
But, she's back to relative normal, otherwise. Stitches come off in a day or two, and then she can finally move on from this horrible ordeal. Surgery and recovery has made her very tired, but she's okay. She's sleeping on my lap as I type this, actually.
The egg was about 5 times the size it should've been. She was unable to pass it after an implosion and 3 separate procedures where they could take out bits and pieces. We were so lucky it was just one egg. I can't imagine how painful that would've been.
End message:
Don't wait if you suspect your bird is egg bound. It can be a horrible thing to endure, both you and the bird. Get it imploded ASAP, induce contractions, warm her up and keep her comfortable... anything to get it to pass. Surgery is a very dangerous option, and it should not be done unless there is literally nothing else you can do (as in my situation). Heavily monitor the bird's environment so she doesn't want to lay any eggs. Just be very careful.
Thanks, all, for your help and advice. The vet process was slow, but it's all done with, and hopefully she can live a happy and healthy life. Though... the next bird is definitely going to have to be a male