If you ever hear a girl say this, it almost certainly means that you’ve made her uncomfortable to the point that she can no longer stand your presence.
When women say this, they’re saying that they’re on the fence about dating a guy. Or, they may legit mean that the dude is a nice person to be around as a friend.
Girls who are talking about guys in this manner often are gauging whether or not they should make a move on the guy in question.
This seems to translate pretty evenly across all genders. When someone says this, they’re saying, “I really don’t want to date you right now. Sorry.”
Depending on how it’s said, it could be that she likes the guy who she’s talking to, or it could be said to remind a guy that he’s taken and that she’s not down for being a side chick.