Hello, my name isXXXXX I can try to help answer your question about Abby.
Sorry to hear about her eye, and her diabetes condition. Does she get daily insulin therapy?
Still dogs with diabetes often get cataracts in their lenses. Were her eyes white and vision compromised prior to the swelling of the eyeball?
These cataract lenses are more prone to luxation or slipping out of their regular place. This causes the normal drainage of the fluid within the eye to become clogged causing the eye to swell (also known as glaucoma).
Unfortunately if this is the case it can be a very painful condition and if not addressed, may lead to rupture of the eyeball itself. Even with medical management we often end up needing to surgically remove eyes with glaucoma.
I have a suspicion that this is the trouble Abby is running into. However, if the eyeball itself is normal size, and it's the tissues around the eye that seem swollen it may be a less severe issue.
Unfortunately seeking veterinary attention is advised.
Hopefully this helps and please feel free to respond with any further questions or specifics.