[Lillith]

I'm sorry you're going through this difficult time. It's hard when they get old.

Most people will say "Better a day too early than a day too late." If you feel your old girl is spending more time in pain and suffering than happy and pain free, it may be time to let go. At this point, I think your feelings are valid that spending more time and money diagnosing this issue is waste, as it likely won't change the prognosis.