The 30-year-old singer and her boyfriend Matt Rutler, 25, reportedly returned to Los Angeles' Osteria Mozza eatery – where they had been drinking prior to being arrested by police on March 1 – on March 4 where they downed wine and left seeming "tipsy". An onlooker told Usmagazine.com: "She acted as if the arrest never happened. When their server offered them dessert, they asked for more wine. She seemed tipsy. "She should see the arrest as a wake-up call, but she doesn't. She doesn’t think things are that bad. She's nearly fall-down wasted nearly every night." Meanwhile, the father of Christina's new boyfriend Matt – who was charged with driving under the influence (DUI) following the couple's arrest – admitted he is "concerned" for his son, but insisted he does not have a serious drinking problem. David Rutler told gossip website RadarOnline.com: "I just feel bad he got into trouble like this, but it could have happened to anyone. He really didn't have that much to drink, he just got caught. Matt was only like .01 over the legal limit ... it's not like he was that drunk. "There are drugs and gangs running rampant in Los Angeles, and they have a press conference about Matt. I'm concerned for both of them. I hope everything turns out OK." However, David went on to suggest that Matt only got behind the wheel of the couple's vehicle because he was looking after Christina, who was described by police as being "severely intoxicated". He added: "He has a perfect record, he has never been in any trouble. He's a good friend, he doesn't leave his friends, he's really there for them, he's a good person to have as a friend and will be that to her."