Unfortunately unless and until SHE seeks out medical help and a diagnosis, nothing can really be done. And even then SHE needs to be the one to seeks out the help and support - and given what you have described about her personality, I doubt she would follow through on these things because it is not an easy process.

I am not saying you should not try. You should do what you feel you should do. But just be aware that you are likely going to be in for a very steep uphill battle - both with your mum and with any assistance you are trying to get for her. And if she decides for whatever reason that she doesn't agree with you, or that she doesn't want to be diagnosed, there is absolutely nothing you can do about it. Anything and everything you will be able to do, will on;y be able to happen with her informed permission and consent, no matter what MI she may or may not have.