It's also a way of dealing with things though, for example you've broke up and arent happy etc and seem to be quite a bit down, I'm not saying she's not upset but by speaking to someone new she's taking her mind off the bad things. Girls are like that they'll move on like nothing then realise what someone meant to them.
I'm not saying that's the right thing to deal with it but gotta be better than being down in the dumps.
Although I'd agree with the not looking thing, that's fine in a relationship but I'd say no not in one, it's given you another reason to feel down when you need to pick up.
Sorry if I seem a but negative though!