My mother has taken first steps towards legal proceedings (MIAM) - help!

[Winter Sun]

I received notice this week my Mum has taken first steps towards legal proceedings, and I have been invited to attend a MIAM. While it's sad, it's not entirely unexpected. Very long story short I divorced my husband a few years ago - since then relationship with my brother and then mum has deteriorated - but important to note that those relationships weren't great to begin with and there is a reason I ended up marrying the person I did (domestic abuse was a feature of my married relationship). Anyway, I have had lots of therapy, as have my children as a result of DA in the relationship with my husband/their Dad. As my mother became more unpleasant (threats to contact my husband, screaming at me, being unkind to the children) I distanced myself. She did not accept that, so eventually I replied saying we all needed space without time limits put on that. She's continued to try and contact me, as well as my eldest child, calling me mentally unwell, asking my eldest if I'm ill because I don't reply. Now I've got an invitation to MIAM. I know I don't have to respond, but I strongly believe mediation won't work - I do not wish to have a relationship with my Mum, the kids don't and we are all concerned about her passing on any info and photos etc to my ex husband. They don't have contact with him for now - he is probably taking the matter back to court very soon now that the year's pause recommended by the judge has expired. I also cannot afford the £130 MIAM fee at all - which my mum will know, and to make matters worse my husband is breaching the court order for maintenance payments but as he lives outside of the UK and its jurisdiction there is not a lot I can do about that. SO i would like to bomb proof myself as much as possible with how I respond to this MIAM - if I don't respond at all she will get a certificate she can then take to court. I imagine she will do exactly that to put maximum pressure on me at a time she knows my ex husband will also be taking me to court. Should I set out the reasons why I refuse a MIAM to the mediator? Even if I could pay, I wouldn't want to try mediation. Thanks for reading!