Khloe is said to be fuming with her brother -- who started dating Chyna earlier this year -- and has only got more upset after news of their engagement, reports people.com.
"Ever since Khloe found out that Rob is dating Blac Chyna, she felt betrayed. This feeling has never changed. After finding out about the engagement, she is furious at the lack of respect," a source said.
"Khloe 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," added the insider.
The source also claimed that Khloe was annoyed that the family wasn't told about Rob's proposal "in advance", and believes her brother wants to cause problems.
"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," the insider added.(IANS)