Hello,I would love to help I just have a few additional questions. After your reply please allow a few minutes for me to type your answer.
Has there been any food changes?
What type of food and water bowel does she use( plastic, glass, ceramic etc)
Can you see any ulcers on the outside of the lip on inside the lip toward the gum?
Thank you for the additional information
Please give me just a few minutes to type up your answer
One of the most common causes of a swollen upper lip is a rodent ulcer however in some cases a eosinophilic granuloma can cause swelling in the upper or lower lip.
Here is additional information on this
The most common reason for these to develop is due to an allergic reaction. Food allergies are often the cause however plastic bowls seems to be the leading cause.
In many cases Steroids is need to clear the problem and all bowls should be changed to glass, or stainless to help prevent this in the future.
While these are the most common causes in a senior cat oral cancer needs to be ruled out so I would suggest having her seen by the vet as soon as you can. Today would be good but if you can not get her in until Monday that should be fine.
I hope all goes well, please reply back if you have additional questions or concerns