If the girl is really hot or has a really unique look, then the piercing will make her even more attractive in a way because it will give her an edgier look. If she's not really hot or does not have a really unique look, the piercing will be somewhat boring. If she is undesirable, it will probably even work against her because it will look like she is trying really hard
The piercing itself doesn't actually do anything to a person's look. It's really more about how it interacts with the rest of their look
Personally I think two things. one: The piercing would be sexy. two: It doesn't really matter if it's sexy or not because you're not trying to bed the piercing, You're trying to get the person to like you for who you are just like you should like them for who they are.
I have never found it hot. It's just not my taste I guess.