Ashlee Simpson has given sister Jessica's romance with guitarist John Mayer the thumbs up, insisting the Daughters singer is "great" for the divorced blonde. Simpson and Mayer have reportedly been an item for the past eight months, despite initial denials they were dating.

The couple recently enjoyed a romantic vacation in Rome, Italy together and Ashlee Simpson insists her big sister is very happy with her new man.

A pal tells People magazine, "Ashlee loves John. She thinks he is great for her. More importantly, Jess is happy."

Meanwhile, celebrity pal Christina Milian is thrilled for the couple: "This is a relationship that's not for the cameras. It's not about celebrity. It seems like they truly have an attraction to each other."