It's difficult to tell if Richard says this because Carol is older, because she's a woman, or both. But the same-sex relationship is not acceptable in society. Richard would probably have a different reaction if Carol were a man.

Carol is right here when talking to Therese, and this recalls the earlier quote about Therese not wanting to clean up after herself. She wants to do whatever she wants without any regard for others, and Therese doesn't exactly grow out of that during the book.

Richard only feels jealous of Carol when he feels emasculated by her.