Can symtoms of CHF/ COPD change quickly ?

My mom's health was horrible when she had the stroke episode on New Year's Eve...fluid leaking from both legs, falling all the time, weight loss, copd, her 4 day stay in the hospital left her not being able to walk ... When she went into the rehab in the NH everything started to get better quickly, one thing she could not smoke... she progressed, gained weight, they got her legs straighten out she started walking with a walker again, was placed on oxygen when necessary. She is out of rehab now and placed in a room. Beginning around the 3 week of February she started having to have oxygen all the time, in full blown CHF (had issues with that for years) is getting where doing anything is a challenge, has had numerous breathing episode where she cannot catch her breath. she is coughing up some nasty stuff. The head nurse suggested hospice and they came and did an accessment on her yesterday. My mom wanted all testing to stop (chest xrays, blood work etc..) that has happened she has told me now more than once she is dying. Her mind is foggy I know from lack of oxygen and the mean, paranoid woman she has been for years is returning again. She had really got where we liked each other and were enjoying each other's company. I went yesterday and she was still in her PJ's which I haven't seen in a long time. How does ones health go from one extreme to the other I do not know what to expect from one day to the next. She should have been on oxygen I know for ahwile but she smoked so much she would for sure have blown something up.Her mental state has changed from bad to alert to bad again. She is starting to reprimand me like a child and is starting to stay mad at me all the time again. I really thought we were going to end this in a better frame of mind but that is declining again.. I am hoping hospice will help us to not go back to what we have always been dysfunctional..I am old enough to know better than to expect a silk purse out of a sow's ear.