The 'We Are Never Ever Getting Back Together' star was initially waiting until she was married to have sex, but was so smitten with the 'Brokeback Mountain' star she went to bed with him after a few months of dating.
A source told RadarOnline.com: ''She thought she was going to marry Jake, that's how in love she was with him.''
However, things stated to go wrong a little later when Jake, 33, didn't make the star's 21st birthday party at her family home in Nashville, Tennessee, in December 2010.
The source added: ''The day before - all was set - he was coming, no issues. But the day of, she doesn't hear from him at all. No texts, no calls.
''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.''
The source says their breakup shortly after inspired her last album, 'Red', in particular the track 'The Moment I Knew', which features the lyrics: ''You should've been there, Should've burst through the door ... You said you'd be here.''
The insider said: ''Her breakup with Jake inspired every word of 'Red'. The song that specifically references this 'event' is 'The Moment I Knew.' They lyrics are all about her birthday party and Jake not showing up.''
Despite the source's assertions, Taylor has previously insisted the track 'I Knew You Were Trouble' from the same album was about another of her ex-boyfriends, Harry Styles.
The 24-year-old star is famous for penning tracks about her famous exes, with her song 'Dear John' widely believed to be about her short-lived relationship with John Mayer. She has also dated Taylor Lautner and Joe Jonas.
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