I'm going to try and keep this fairly succinct and get to the aibu - or you can skip to the TL;DR!
Throughout my childhood my father was occasionally physically and frequently verbally violent/abusive and my mother enabled or ignored it. I moved out and away by 18yrs old and went very limited contact until in my late 20s which was when my mum made a lot of effort to get along and somewhat acknowledged my dad's behaviour. My dad however has no redeeming features and is an odious gammon who spends all day spitting with rage about 'bloody immigrants and foreigners' and the likes.
Fast forward to an argument while at their house which started with my dad being rude to my (absolutely wonderful) partner and me calling out his rudeness. My dad sneered and accused my partner of 'clearly not being able to handle looking after a child' because he made a clumsy, harmless mistake, not to do with our young dc but while distracted by attending to them. I saw red and pointed out that this was coming from a father who punched his children to which he said he'd never laid a finger on us and I'm making it up, that I'm not right in the head etc.
I decided to just pack up and leave. My mum wailed about how cruel I am, that I'm punishing her by taking away her grandchild, want her to die alone and I'll regret it when she's gone (highly doubtful). I said she is welcome to visit us and see her grandchild anytime at all but without my dad which she said she won't do because she doesn't like going anywhere without him. She drives and is completely physically healthy, we're 1.45hrs away by car, 2.5hrs by train.
AIBU to put the caveat on her seeing us of coming alone?
TL;DR my dad is an absolutely vile man so I only want to see my mum on her own but she won't travel without him which means she won't get to see her grandchild.