Hi Lucy's mom!
I'm sorry you girls are going through such a hard phase. To answer your main question, yes I think that teething can throw every sleep training advance through the window. It can switch an angel baby for a really grumpy one. I've seen cases around here where all the molars pop out at once (as your case appears to be) and the sleep goes to hell. She's too young to manipulate you, I think if she's waking for 2+ hours at night, it is clearly something bothering her. She might be in horrible pain, so I'd suggest you to try pain meds approved by your ped before bed and in the middle of the night if she happens to have a bad night waking (one with hysterical cries etc). Check also with your ped the dosage cause she might be needing a 2yo dosage instead of a 1yo. That should help you with the long night wakings.
As for going down, I think you did a successfull sleep training but got stuck in the middle of it. I understand how hard it is and how vulnerable we are first thing in the morning (especially with such an early morning!) but I think that you're only missing the last step and it will be so worth it even if you have to have a couple of rough weeks. Your husband's right, she's getting mixed signals, cause she knows what to expect from grandma and dad, she knows she won't get the breast so she's ok with it, and it is extremely important that she gets the fact that she will get loving and nurturing from you in other forms different than your breast, cause you're the person that spends the most time with her, so she should be able to go down easily for you more than anyone.
You can stop cold turkey from feeding her and taking her to your bed. Stay by her side in the crib, you can do that either standing there patting/reassuring her once she wakes or you can go back to sleep (if you can!) in a blow up mattress/sleeping bag. LEt her know those early hours in the morning are for sleep and make sure she's not in pain either that early in the morning (the meds might have worn out by then) or when going down for her nap (she might need another dosage then). I think you're facing a mix of pain (and the clingyness and upsetting it brings along) and remains of the accidental parenting you did in the past.
Fortunately it looks like you guys have come a long road and i don't think it'll be hard to settle her if you remain consistant for a couple of weeks and have her in the right dosage of meds. Once the teething stops it will be more easy (if not, not necessary) to continue sleep training her.
Good luck, HTH and keep us posted!