It's very common to have a fetish, I think most people have at least one kink in them. I don't have any numbers but I think foot fetish is pretty uncommon but no unheard of. If you surround yourself with a fetish it is pretty normal to start to think that everyone is into it, but they aren't.
If you instantly go for a girls feet, yeah she will think you are weird.
But if you tell her in advance she won't think you are weird. If you find it embarrassing to say, have sex with her once or twice and ignore her feet until you are more comfortable.