According to a source, she took Traumeel, a homeopathic medication. "She became worried about breathing, which is why 911 was called," says the source. Adds another source: "She was apparently distraught over an argument with her boyfriend."
The singer has been released from the hospital and her father Billy Joel is now with her, says a source.
Being prone to emotional highs and lows was nothing new to the singer – and she spoke candidly about her frustration with relationships.
In August, the singer took to her MySpace page to vent about relationships, writing, "UGH!!! MEN!!!"
She continued: "Is anybody else finding it a difficult "dating world" out there? I'm so terrible at dating – I don't know if I'll ever get used to it! And I HATE the game-playing! Can't stand it.
I live in the greatest city in the world and I can't seem to meet an interesting guy who also happens to be NICE. Go figure... "
Alexa Ray admitted to PEOPLE last year, "I can get very dark. I can get very in my own head and depressed as many other artists can."
But the singer/songwriter typically channeled her emotions into her music.
"I was crying all day. I thought how am I going to put on a show," she said about a previous breakup with her former bass player Jimmy Riot. "[But] the minute I got out there, it was the best show. I thought I was going to break down, and suddenly this energy with all the emotion was just pouring out."
Reporting by LIZA HAMM and LIZ MCNEIL