Meeting your new boyfriend’s mother can be nerve-racking — especially if she’s Diana Ross. Rather less iconic singer Ashlee Simpson, who’s dating Evan Ross, met Diana for the first time at Aventine Trattoria in LA Saturday night. Simpson was introduced to the Supremes diva after her one-night performance at the Hollywood Bowl. She sat with the Ross family at the restaurant, where a fellow guest overheard Simpson saying that she was “nervous . . . but Diana is wonderful and very open.” Simpson and her beau, who have been dating since June, were spotted dancing and kissing, and were overheard talking about traveling to Europe together soon.