Khoé Kardashian still feels betrayed by Rob

Khloé Kardashian isn't going to be celebrating her brother Rob Kardashian's engagement to Blac Chyna any time soon, a source tells WHO.

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"Ever since Khloé found out that Rob is dating Blac Chyna, she felt betrayed," the source says. "This feeling has never changed. After finding out about the engagement, she is furious at the lack of respect."

Rob, 29, proposed to Blac Chyna, 27, on Monday – with the news taking the family by surprise, says the source.

"She can't believe Rob didn't tell the family in advance. She thinks Rob is causing drama on purpose and wants them [his family] to be arguing," says the source.

Khloe and Rob. Photo: Khloe Kardashian Instagram

So far, Rob's sisters and mother Kris Jenner have remained silent concerning the engagement.

"Khloé plans on ignoring the news. She is not going to send Rob any well wishes. She is not happy about the engagement, and is not going to pretend that she is," the source adds.

For more on Khloe Kardashian and her new fears for Lamar Odom pick up this week's issue of WHO - on sale now.

A source previously told WHO the Kardashian-Jenner clan was concerned about Rob's relationship with Blac Chyna.

"There has been a fear that Blac Chyna is manipulating the situation with Rob," said the source. "That he is getting himself into a situation that is not ideal for him. Blac Chyna has been great as kind of a rebound. As someone that got Rob out of a dark place, that helped him get motivated and healthy again. Let's just be honest, no one is really hoping for a marriage to happen."

Khloe Kardashian on Easter Sunday. Photo: Getty

Khloé has previously been vocal about her support of Rob, who lived with her as he struggled with depression and weight gain before returning to the public eye with his relationship with Blac Chyna.

"Rob is such a great guy," Khloé, 31, told WHO in October, before the relationship with Blac Chyna. "He's charming, charismatic, everything. That's what's so infuriating. I'm like, 'Where is your will to live life? Let's be around people!' "

For her part, Blac Chyna has a complicated history with the Kardashian-Jenner family, sharing a child with Tyga, who is dating Rob's sister Kylie Jenner. Blac Chyna is also best friends with Amber Rose, the ex of Rob sister's Kim Kardashian West's husband Kanye West.

Khloe and Rob. Photo: Khloe Kardashian Instagram

Blac Chyna's rep previously dismissed the idea there was "any tension" with the Kardashian-Jenner family.

"I think everyone's happy about it," the rep told WHO of the engagement. "I would imagine people would be happy for their family when they find the love of their life."

Aaron Couch writes for People.