I think forcing them to befriend him when they obviously don't want to is a very bad idea, and won't work out for him at all.
I do think, though, that when children don't like another child, and when they spend time speaking to their friends about him (especially if those friends are bullies) there's a sense in which innocent behaviour gets vamped up and made to sound 'urg creepy' when it really isn't, because it's kind of a conversational currency.
I don't know if that makes sense, but I remember doing it, and I've heard girls doing it in groups too. So if the boy no-one likes looks over at you, when you're picking him apart in conversation with your friends who you know don't like him, it ends up being 'OMG did you see him totally staring at me, he's so weird, I think he's a murderer or something, he's such a perv' etc.
I'm not saying your dd does this, but I'm not saying she'd be an unusual child if she did, either. That's how The Kid No-One Likes gets talked about, sadly.
What would concern me is that a) her friends are bullies - how long will she be safe for, if she doesn't join in yet? and b) this child is genuinely lonely and unhappy, and the only reason given for his unpopularity is that his parents have just divorced.
I wouldn't be telling her she must start being his BFF, but I would be encouraging her to reflect on her friends' attitudes, and her own, too.