Lindsay Makes Splash at Betty Premiere

At Monday night's Ugly Betty premiere in NYC, Lindsay Lohan was comfortable and relaxed in an Alexander Wang mini-dress as she pozed for photographers on the red carpet outside Highbar.

Then, it was up to the rooftop, where an eyewitness tells OK! the actress celebrated and  seemed in good spirits, taking pictures with fans and happily showing off a diamond band on her right hand and a new star tattoo on the inside of her wrist.

Lindsay recently told Marie Claire's October issue, "Samantha Ronson has a bunch of stars, so I got that."

Lindsay had more than one reason to celebrate--it was also her mom, Dina Lohan's birthday--her eventual reason for ducking out of the party early.

Lindsay's co-star on Ugly Betty, Eric Mabius, told OK! the actress was "fun to work with" and that "it was nice to see her girlfriend Sam visiting the set and offering her that support."