As a girl, I'll answer it from female perspective. I wouldn't mind my guy hanging out with girls. However, I'd be careful of what may happen. But if he hanged out with one specific girl, then I'd become jealous although I wouldn't show it. If I have a reason to suspect, I'd start to investigate. There you go :)
It wouldn't be a deal breaker, but I find it as a red flag. If she can't get along with people of her own sex, what does that say about her? She might not be friends with women because she thinks they cause too much drama, when she might be herself.