Kim Kardashian is reportedly bitter that Khloé is living the "high life".
The 33-year-old star gave birth to her daughter North with Kanye West in June last year and married the rapper in Italy in May.
Now things have calmed down for the reality TV icon and she's apparently envious of younger sister Khloé and her romance with French Montana.
"Kim loves being a mother to Nori and her wedding was one of the happiest days of her life, but now the buzz has died down, so has her happiness," a source divulged to British magazine Star.
"She's envious of Khloé getting so much attention and living the high life with French, while she's been home alone as Kanye is constantly travelling for work.
"The jealousy has been getting her down. Kim feels sidelined as she's found herself alone a lot."
The whole Kardashian clan are known for loving social networking and are frequently posting selfies on Twitter and Instagram. However, it's thought to have become more than a bit of fun for Kim.
"Kim and Khloé are trying to one-up each other - it's an all-out Instagram war! They compete to see who gets the most 'likes' and feedback on their posts," the insider continued.
It was recently reported that Kim misses Kanye, 37, a lot when he's away. She's apparently worried he won't be around for one-year-old North's important milestones.
"Kim is really sad. She finds it hard when they're apart, not just for herself but for Nori too," a source said.
"Kim doesn't want Kanye to miss their little girl's important moments, but the reality is that he's a very busy man and can't be there all the time."