What can i do to help my mum?

Wow what a tough situation. You sound like a wonderful daughter, and it is so sweet that you are so concerned for your mother. My suggestion? There are SO many different types of anti depressants that are out there, she should not get discouraged just trying one that doesn't work for her. She just tried the wrong one. Also, she may want to try something that will treat anxiety as well... sounds like she could have anxiety as well. She is very lucky to have you!