You should tell her how you feel and if your goals don't align then you need to move on with your life and find someone who's more compatible. I know a couple of people who are very open about sex and often don't see it as intimate but more general like you can do with anyone. I'm not going to comment on whether it is right or wrong, I know there have been studies found on this type of relationship or whether your girlfriend truly loves you but again, I don't know enough about the topic to comment on this. I know there are a lot of people myself included that would find this kind of behavior unacceptable but she did sort of talk to you about it and you did (unintentionally or intentionally) agree to it.

Yea talk to her, don't just assume she's a slut or a terrible person but just tell her you changed your mind, you really still love her but you are not comfortable with this anymore and if you feel you need to break up, just break up. It's going to hurt and feel like a bitch and you are going to doubt whether you made the right call but you're gonna stop feeling like this eventually and eventually, you got to start dating again. You may not find a supermodel but I'm sure there are enough girls out there that will make you feel happy and fullfilled in your life. Sex is such a small part out of any relationship.