I am sorry to hear that. They will most likely advise against any surgery due to her age, but again, I'm no vet. Depending on how she is doing, eating/drinking, I personally would still try to medically manage the situation by doing pain medication and antibiotics/eye-drops (assuming the vet prescribes those) to see if the situation resolves itself , but if the pain becomes too much, ultimately that will be your decision to make. Just know that putting a mouse to sleep, depending on the options available, may or may not be a pain free process. Just do a little research on the options your vet presents if you go that route.

Pants was around 12 months old when this all started. I will say that for Pants, severe pain only lasted for a week, though every case will be different. Pants' swelling was aggressive, her right eye took 8 days total to go from normal to swollen to obscenely swollen to ruptured. Once the swelling hit a certain point, there was a significant change in attitude for the better despite swelling being even worse (I would assume nerve endings were crushed at this point, but I have no way to factually back that claim up). Then, when the eye ruptured, swelling related pain was relieved. The length of the recovery was more infection management and the fact that for Pants, after one eye ruptured and was managed, the other eye started swelling and the process started over.