My cat fought a dog, face swollen and bleeding. Should I see a vet?

I am sorry to hear about Stitch. Based on your description I would recommend having her examined by a veterinarian as soon as possible. I would be concerned about possible head trauma/brain injury, injury to the eyes which can be very delicate and if left untreated can result in permanent damage/loss of vision. It also sounds like she has significant swelling of the face. This is likely very painful even if your cat is not showing obvious pain (cats are very good at hiding pain) imagine if you had been mauled as your cat had. The vet can prescribe pain medication to help Stitch feel more comfortable, antibiotics if needed to prevent infection, and may also booster Stitch's rabies vaccine if it has not been done recently and this dog is of unknown vaccine status.