TBH I don’t think there is a right or wrong here.
Your DD isn’t obliged to like this bloke, but equally you shouldn’t feel forced to stop seeing him, especially if she just declares that she hates him and won’t say a word to him.
If she genuinely doesn’t like him and there’s a reason, then she needs to tell you that reason so that you can talk about it, but at the moment she is behaving like a petulant brat, and I would tell her that you want to talk about it, but “I hate him” isn’t ok to say just “because”.
My DC severely dislikes my ex’s partner. But part of the reason for that was that she practically moved in from the outset, made her own daughter the centre of his world and insisted they were siblings now and they both got annoyed if the kids fell out, which is actually normal sibling behaviour… Later on she took to slagging me off on a regular basis.
DC spoke to ex about it, who dismissed their concerns entirely, got this woman pregnant and moved her in straightaway.
The upshot was that DC never stayed there again. Now ex admits that it all happened too soon, and even says that having another baby was a mistake.
But the difference here is that DC talked about his concerns, and they were just brushed off.
If your DD genuinely doesn’t like this man then she needs to tell you what the problem is so you can talk it through, and deal with it if necessary.
If there is a genuine reason why she hates this man, then perhaps the relationship is doomed, but if not then while you might not want to think about living together for now, she does have to realise that you are entitled to happiness as well, and she won’t always be there.