Can I tell off this girl?
What did the girl do that makes you want to tell her off?
She's acting as if it's "normal" to date a guy who has already dated multiple people.
I don't think the girl is at any fault. It's just a matter of opinion and she believes it's fine so you should respect her decision. You shouldn't force others or reprimand people for having different beliefs or opinions as you because it makes you look ignorant, controlling, and narrow-minded.
I think all people should date as many people as they can before they settle down. It doesn't matter who the person is and if the first was bad doesn't mean the next will be since no relationship is bad or good.
It sounds like you agree with her? She wants to date a guy who has already dated multiple people, and you are now saying it is okay to date multiple people before you settle down. Allow this girl to do what she wants and don't force her to accept your beliefs.