Khloé has been linked to rapper French Montana since the beginning of this year, with her family thought to be worried the musician wants to use her worldwide fame to gain popularity.
During a recent interview with Billboard he admitted as much, but Khloé (30) dismissed his comments in a Twitter post.
Now it's believed Kim (33) is fearful her younger sister stands to make a fool of herself.
"Kim was always the most wary of French, but everyone decided to give him a chance," a source told British magazine Star.
"Now he's said these things, Kim's told Khloé she should have more respect for herself and that she's selling herself short."
In the interview, French (29) revealed he was willing to "capitalise" on his girlfriend's fame in order to boost his own career.
"I’ll get a fan base from everywhere. I just hope I’ll be able to connect with everything that’s going on," he said.
The reality TV star hit back on Twitter with: "It's amusing to me that Y'all think I don't see it. I was the first one to see it. I just don't care. (sic)"
Her family are reportedly surprised that's the stance she's chosen to take.
"His interview has left a sour taste and they're baffled by Khloé's defiant attitude," the insider continued.
"The family is used to people trying to exploit their fame for money, and this is humiliating for them. Ultimately, they're worried Khloé will end up getting hurt.
"That's the last thing they want to see after her painful breakup with Lamar [Odom]."
Khloé married basketball star Lamar in 2009 but she filed for divorce last year after rumours he had been unfaithful and was taking drugs.
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