Its hard to cope with hurtful comments whatever the situation is.It can be hard even if you don't care about the person who made the comment.All the more hurtful if it's a family member who you love.I'm sorry that your situation is so bad and that you are struggling to cope.
I'm just somebody who has paranoid schizophrenia,not a Doctor or anything of that nature.
There have been some huge changes in your life and for your mum too.You mentioned that your partner thinks the world of your Mum.And that when they are together she is fine with him.In my opinion these things are good.At least this is going right for you.
Your Mum's hurtful comments may be because of her illness.I know that I get 'symptoms' more frequently when I am stressed out;and that's usually down to money worries.Stress triggers my illness in a big way.
I can't understand why your Mum is resentful towards your partner when it was the man in your previous relationship who didn't want you to spend time with her.
I do hope your Mum's financial situation improves.I know what it's like to have to live hand to mouth.Recently I've been tempted to steal meat from the supermarket because we are really struggling at the minute.
I note that you say no amount of reassurance works and that sometimes you have to bite your lip.I'm sorry that this is so.Maybe your Mum is experiencing delusional thinking.Paranoid thoughts etc.Is there any way to get her stress levels down?