By Phillip Matier and Andrew Ross
San Francisco Mayor Gavin Newsom's new squeeze, Brittanie Mountz, just turned 20 last month -- and that raises a couple of questions about the couple's nights on the town. The biggest question is whether Mountz has been drinking, and it's been swirling since the pair made their first public appearance and walked down the red carpet together at the San Francisco Symphony in September. At the time, Mountz had a MySpace page that said she was 19. It now says she's 26. But according to the Sonoma County registrar of voters, the Rohnert Park resident turned 20 on Sept. 17 -- three weeks and two days before Newsom turned 39.