Singer Selena Gomez Arrives at the 2014 Vanity Fair Oscars Party in West Hollywood
Her grandfather Ricardo Gomez told the press that the young pop star was suffering from lupus since several years but is getting along well with the treatments. REUTERS

Former Disney star Selena Gomez was boozing it up during the Vanity Fair Oscar 2014 after party and was spotted "drinking and stumbling all over," according to eyewitness. After a short stint in rehab, the "Come and Get It" singer got wild Sunday night at the 86th Annual Academy Awards with "Spring Breakers" gal pal Vanessa Hudgens.

According to a RadarOnline source, Justin Bieber's ex had a little too much fun and was "boozing it up and stumbling" out of the event. While at the Oscars' biggest after party, the 21-year-old star sipped on champagne and other drinks that could have been vodka or gin while hanging out with the "High School Musical" star. The two Disney buds took a lot of photos while goofing around.

"Selena was drinking constantly throughout the entire party when I saw her," according to Radar's eyewitness. "She was having a grand old time and towards the tail end she was stumbling in her heels and almost toppled right over."

After checking herself in rehab because of exhaustion, Selena is back partying and just having fun after dealing too much drama with her breakup with Justin Bieber. According to a source of MailOnline, Selena was never photographed with a drink in her hand and "She wasn't even there very long."

While at the party, Selena posted an Instagram photo with friend Vanessa and captioned, "My only, official party buddy for life ;)"

"Selena and Vanessa were just having a really good time, laughing and taking pics," says the source. "She wasn't slurring too bad, but was definitely in the happy-sleepy stage."

Monday morning after the Vanity Fair after party, the gorgeous brunette was spotted looking just fine without a hint of a hangover as she headed to a dance studio in L.A. The night that she allegedly let her hair down, ex-boyfriend tweeted her stunning Oscar style and captioned the photos, "Most elegant princess in the world."

The unexpected tweet came after the "Beauty and the Beat" did not invite Selena to his birthday bash after she went to a date with One Direction Niall Horan. The two were last seen together in January having a good time while riding Segways and posted an Instagram photo as they embraced each other.