Are you in the US? Just cause I can’t speak for other countries. I’ll assume you are.
I’m on disability for PTSD and Bipolar disorder. It is not easy to get. I had five different doctors writing letters for me, and was still denied for several years before it was finally approved. They don’t care what condition you have, you will not get approved based on just that for any condition. They want to see how it impacts your life, and they don’t approve it if they think you are going to get better eventually.
You ask how she will get a job; she probably won’t, and if she does she won’t be able to keep it. That is the nature of disability. I had a 25 year work history where the longest I managed to hold onto any job was about a year. Most were less than that. If I could get and keep a job, I wouldn’t have been approved for disability.
Professionals who know the details of her condition much better than you do have determined she can’t maintain gainful employment. That ought to be good enough.