The singer got engaged to NFL player Eric Johnson last week after a six-month romance and she is now determined to walk down the aisle before her ex-husband Nick Lachey.
Nick announced his engagement to long-time girlfriend Vanessa Minnillo a few weeks before Jessica became engaged.
A source said: "She wants to beat Nick to the altar. She knows that it is going to be tough to pull everything together on such short notice, so it might have to be a New Years wedding.
"In any case, she wants the focus to be on her wedding. She doesn't want her wedding to be the aftermath of his."
Sources also claim the Come On Over singer will spend a fortune on her big day as she doesn't want to be upstaged by Nick and Vanessa.
The insider added to HollywoodLife.com: "It will be big and elaborate. She'll spare no expensive for fear that Nick and Vanessa will outdo her. She's already starting planning everything and has every family member working on her big day."
While Jessica is planning a Christmas wedding, it has been reported the blonde beauty is refusing to make her fiancé sign a prenuptial agreement to protect her $100 million fortune, which has angered her father-and-manager Joe Simpson.
A source said: "At the moment, Joe is sitting back and being a great father supporting his daughter and his future son-in-law.
"However, you can bet after all the excitement has died down, Joe is going to do everything in his power to make sure Jessica doesn't walk down the aisle until Eric signs away any right he might have to Jessica's enormous fortune."