tessalyon I'm so sorry about what you're going through. I know it's hard and I know you don't want to hear those words from people, but really, they don't have anything better to say, or they don't know how to or which words to pick. 15 years is A LOT for a dog and I really hope she will live more. No one can really tell you what to do, it has to be your decision. If you feel she should have a surgery - give it a go. I know I would if I felt that about my dog - you know her the best. Sometimes animals amaze us. Recently my friend's dog had a huge tumor removed, vet gave him less than 30% survival chance because of his age, but he made it. On the other hand, if she doesn't make it - she won't suffer, it's going to be like putting her to sleep. Hang on there.
Respect and you shall be respected. Animal is always right.