My 7 year old Shih tzu has had knee surgery and now has pnuemonia, her chances for surviving are bad right now?

almost 3 weeks ago my doggie had surgery on her knee and ACL. She was doing well until the other kneee went out and she became too nauseas to take the antibiotic anylonger. We took her off the antibiotic to stop her vomitting and now she has a severe pnuemonia. She stayed in the hospital last night on IV antiobiotics to try to fight the illness. Her chances are slim. Has anyone else been through anything like this before I am devastated at the mere thought of losing my precious Roxy.