Good chance chad will get her pregnant and then do a runner. Alternatively she finally fesses to the bf or the chad (who now knows who’s gf he is fucking) does and they split up.
Poetic justice would be for the bf to bump into her 5 years down the track after moving on and her being single as chad has moved on to new conquests.
Edit: I must admit it was really funny when chad worked out who’s gf he as fucking and then just goes, fuck it, and starts another round. A real keeper that one!