“Keeping Up With the Kardashians” star Kylie Jenner is upset with Tyga for going to his former partner Blac Chyna and talking to her each time the teenager and the rapper have an issue. Jenner is even more worried that Chyna may write a tell-all book with the information she receives that could ruin Jenner and Tyga’s relationship, Hollywood Life reported, citing a source.

“Kylie thinks Blac’s an opportunist and it upsets her that Tyga runs to his ex when they’re having problems, telling her everything that’s going in their relationship. For all Kylie knows, Blac could be taking all that information and plotting to write a book, exposing what goes on behind closed doors with Kylie and Tyga. She doesn’t trust Blac. She feels that woman has some sort of spell over Tyga, especially since they’ve had a child together,” the source said, according to Hollywood Life.

The insider also said that Jenner, who turned 18 in August, is concerned Tyga may cheat on her with Chyna. Tyga and Chyna have a son named King Cairo. Since the “Rack City” rapper started dating Jenner, relations between Chyna and Jenner have soured.

“Kylie also feels Tyga has the propensity to get weak around her and it would break Kylie’s heart into pieces if he cheated on her with Blac. She wants there to be little to no communication between those two. And whenever Tyga has to drop off King at Blac’s house, Kylie will be right there,” the source reportedly said.

Despite the latest report by Hollywood Life, there are ongoing rumors about the couple’s engagement and preparations of a wedding.