Here are some lines that might help you navigate a difficult conversation:
“You’re better than that”
Challenge their comments in a non-confronting way.
“Mate, what if that was your mum or sister?”
Highlighting someone close can make it more relevant to the person.
“It’s not cool to say that. She has the right to wear that / say that / do that”
Remind them everyone has the freedom to make their own choices.
Asking a question can help people think about what they said and its impact on the person.
Talk to your mates about it... When sexist comments or behaviours occur point it out to your mates and start a conversation.