Mitra Valve Prolapse

My mom is 91 years old.  She has mitra valve prolapse.  At one time about 8 years ago she did develop endocarditis.  But survived and has been doing well till now.  She had trouble breathing and took her to the hospital and were told she had a touch of pneumonia.  She was kept for a couple of days and given antibiotics and then released.  The nurse came to check her out today and said she still feels she should be on an antibiotic for the pneumonia.  She has also been put on oxygent (2) whenever she is walking but now while she is sleeping or sitting.  I am so worried will she get better?  How can we tell if the mitra valve prolapse worsens.  Please give me some idea what to expect.  Thank you.