My girlfriend arrives early and catches me having sex with her mother

My mother-in-law and I have been keeping a sex-only relationship a secret for quite some time now and we both know it will never happen because she and I are in love with our respective partners. the problem is that during our last intense sexual encounter, my girlfriend came home early and surprised us in the middle of the action, which made her feel a lot of anger that her mother was able to mitigate in such a way that she ended up masturbating while he watched his mother and I fuck like hell.