I know how hard to watch your mom suffer.
It sounds like she might need an anti inflammatory medicine since it is so swollen now. She might even need an xray in case she somehow injured it.
There are different pain management techniques such as a patch that might help her more.
Call her doctor in the morning and discuss this with them. Don't let them not do something to help her tomorrow.
A hot water bottle could be comforting but not when she has ben gay on. Also don't use a heating pad due to possible decreased heat tolerance due to diabetes.
If the vicodin is prescribed for her then give it as prescribed.
Do try to get her in tomorrow and at the least have them give her something else for pain.
God bless you both,