Speaking to heat magazine , she said: "Beyonce has been encouraged to write about the affair rumours to help her deal with it all and help her determine whether she could work through everything or have to end the marriage.
Shanica appeared to hint that her cousin has had to deal with her man being unfaithful, claiming she has been furious but is "learning to forgive".
She added: "She's been through the intense anger and I think she's now learning to forgive Jay.
The next few months are going to be the test - this is make or break for them - but he's determined to do everything she can to make it work."
Her comments come after Jay chose not to attend the annual Met Gala with his wife , despite the recent claims about their relationship.
The rapper's absence from the red carpet on Monday night only added fuel to the fire, but according to an insider, there was no dramatic secret behind his decision.
"He's done it before,” a source told Us Weekly . "There's just no big reason for him to go."
