Oh your poor Mum! She sounds as though she would definitely benefit from counselling.
Her trauma however should not change your plans though, you should be able to birth wherever you feel safest, because that is extremely important.
I would definitely just keep my plans a bit unclear, and just birth at home regardless, if that's your decision.
I wouldn't have her meet the MW or anything, it's your birth, and you have enough to be thinking about without trying to put your Mum at ease. She needs to see someone else for herself if she chooses to.
She wouldn't be someone who you would want to be present, as the people you need around at a HB are those who are positive, calm and collected.
I hope everything goes well for you, and your Mum somehow manages to process her trauma.
All the best