How can I be more forgiving with MIL

[menopausequeen]

Name changed for this

I am middle aged and have been married to DH for 25 years. I have known his family for about 30 years.
When I was young and first married I tried so hard with his family (my DP both died when I was in my 20s) and they were fairly mean to me. Laughing behind my back, dismissing my views, undermining me etc. I was very different to them - degree educated and in a professional role (which they never ever asked about) and they were very much no ambition. Im
not saying that’s wrong but whilst I tried to appreciate their views and lifestyle they did not give me the same courtesy. They weren’t very nice to my DH either at times as he was ambitious and achieved a lot on his own (no support or encouragement from them).
Anyway fast forward a good few years and mil is elderly and widowed, much nicer to me, in fact goes out of her way to ask about me and is positive about me and the way our dc have been brought up. The things I cannot forgive her and I have a real dislike of her. Even when I hear her on the phone I shudder inside and have to grit my teeth to ask about how she is. I see her the minimum amount possible.
i have 3 ds myself and i know being a mil is hard and I’ve probably made mistakes and will
make mistakes with my sons partners but I just cannot move on from my feelings about how mil treated me.
i know I need to try harder but does anyone have any tips on how to do this, it’s becoming a real issue and I know I am being unreasonable but just can’t change how I feel!

I don’t think I can talk to her now because she’s old and presents as mentally frail and would get very upset
I I have tried to discuss with DH to get some validation of how I felt for years. He’s very much of the opinion I need to move forward and she won’t be around much longer (she could easily be around another 5 years as she’s physically resilient despite her age )
she plays DH and his siblings off against each other so maybe more mentally astute than I give her credit for

I agree with the poster above that you sound very kind and thoughtful.
There is a big difference between 'mistakes' wrt family members caused by genuine misunderstandings or miscommunication and being deliberately nasty, undermining and deliberately playing her children off against each other. That is manipulative and emotionally abusive.
From what you have said here, she is just an unpleasant person so your gut reactions to her are only natural. The fact that she is elderly and now widowed does not mean that she is suddenly a completely different character. Her circumstances have changed so she is changing her behaviour to try to take advantage of the new ones. Your DH is entitled to forgive and forget, she is his mum after all, but he should try to understand your feelings and not dictate how you should respond or behave. That is wrong of him.
If you had said that she apologised to you for her previous behaviour many years ago, given you some kind of explanation and been a loving and kind MIL for years, I am certain that you would have been able to move on. It is far harder to do so when the situation has never been discussed and no apology has been given.

This. I came to write about my experience with abusive in laws who turned nice when they became frail and ill.

If they'd been kind and accepting instead, I'd have done anything for them. Now MIL has died & FIL is frail and just been admitted to age care. I won't even bother to see him unless unavoidable for DC sake. He's so nice to me now, but it's purely vulnerability talking. I wo8help. DH has to wear that as he knows he didn't stop them earlier on. I cannot forgive.

It's a completely understandable, human response.

Your MIL is reaping what she sowed. You don't need to welcome her with open arms, she isn't the prodigal son.