Is she limping at all (holding a leg up), or is it only the hunched over posture?
Is she drinking water?
Lift her lip, what color are her gums?
It sounds like she has injured her back. It probably occured when she jumped the gate. Back pain can be particularly penetrating, and makes it hard for them to get comfortable. For tonight, I would recommend giving her aspirin at a dose of 5mg per pound. So if she weighs 15 pounds, you can give her an 81 mg aspirin. I would recommend using the coated variety to help protect her stomach. This dose can be repeated in 12 hours. If she is still uncomfortable tomorrow, I would encourage taking her to see her vet.
Also, keep her quiet, and don't let her run around. It could worsen the pain. If she starts walking like she is drunk, or starts dragging her hind legs, she needs to go to an emergency clinic immediately.
I hope this helps.
Thank you so much, I can't tell you how much I appreciate it!
You're quite welcome. I hope that Abby is feeling better very soon!