People love to say this, but I saw just about every male on the beaches in Nice and Cannes leering at the topless girls when I was there. Italians, Spaniards, Frenchmen and of course the tourists like myself. They’re all out to get an eyeful, don’t fool yourself.
They’re not leering at the girls because they’re topless. They’re leering at them because they are girls, tops or not. Same thing happens at any beach in the US, we just don’t get to see as much.
There’s scoping a chick out, and there’s leering. It was a bit creepy, but I suppose they could’ve just been creepy euro-dudes in general hehe. I was just commenting that it’s not like just because it’s more frequent to see topless women at a beach in Europe that it’s not going to make a difference to wear one or not. I also saw lots of very attractive european ladies wearing tops. I’d say that the non-elderly fit women were the minority in the topless category actually. Of course it was only a few days one vacation so who knows. I’ll need to take more vacations in southern France and Spain to be sure I think 
People don’t walk around naked for the most part, why would a certain beach make any particular difference for a person? It’s a personal choice that shouldn’t really matter, but I’d wonder what the OP’s GF is doing it for. It’s not a requirement to fit in obviously, maybe she just wants to try it out because it’s out of the ordinary for her? Maybe she’ll change her mind when she gets there and sees said creepy guys. If she does it and it bothers you break up with her, at least then you have other nekkid ladies to go say hi to… 