It depends on who they've had sex with.
A study found that women are more likely to leave a man if the man's had a homosexual affair, while men are more likely to leave if a woman's had a heterosexual affair.
So a woman cheating with a woman is less risky for the relationship than a woman cheating with a man.
And a man cheating with a woman is less risky for the relationship than a man cheating with a man.
This may confirm Darwinian theories which suggest that men fear infidelity because it might lead to a partner carrying another man's child, while women worry that a man preferring another man is more likely to lead to her being abandoned and unable to successfully raise the children.
My Guy’s Cheating with a Man? I’m Outta Here. Newly published research suggests whether infidelity ends a relationship depends in part on whether the affair was gay or straight, Miller-McCune>>