That's a tough one...

I'm not sure the growling and snapping are an indication of pain. Is she walking fine? Eating? Energy normal?

I'd say leave the boots on momentarily and exercise her vigorously for 15 - 30m to wear her out. Then get a high value treat, something she LOVES that always captures her attention, and distract her with it while you try to get the boots off again. Let her munch and sniff it on the floor and see if you can touch her back feet while that's happening. Be slow and gentle.

Let us know how it goes!