Taylor Swift is notorious for writing songs about her exes. And probably her most famous ex of them all is none other than Jake Gyllenhaal. Now, a source close to the singer approached RadarOnline and spilled intimate details about the two's relationship.

According to the insider, Swift, who was 20 when she was dating the actor, had been saving herself for marriage. But after dating Gyllenhaal for three months, Swift decided that he was the one and gave her virginity to him.

The source said, "She thought she was going to marry Jake, that's how in love she was with him."

But shortly after the two got it on, the singer threw herself a birthday party in December 2010 at her family's estate in Nashville. Of course, she was expecting her one true love to make an appearance at her bash. But it seemed the actor had other plans at that time because he was a no-show at the party.

"The day before - all was set - he was coming, no issues. But the day of, she doesn't hear from him at all. No text, no calls," the insider added, "Taylor thought maybe he was planning some sort of surprise. Nope. He didn't show up and she locked herself in the bathroom and cried the entire night."

Perez Hilton reports that their relationship inspired the lyrics for Swift's 2012 album Red. The song that particularly captures the events surrounding the singer's birthday party is "The Moment I knew." With lines such as "You should've been there," "I've got my eye on the door, just waiting for you to walk in," and "And there in the bathroom, I try not to fall apart," the song appears to be a blow-by-blow account of Swift's disastrous party.

But last year, Swift told US Magazine that Gyllenhaal was aware that the album was about him. She said, "He was like 'I just listened to the album, and that was a really bittersweet experience for me. It was like going through a photo album.' That was nice. Nicer than, like, the ranting, crazy e-mails I got from this one dude."

As to her side regarding the insider's revelations, Swift's representatives have yet to comment on the matter.