There are two main models or approaches used by therapists to help both sex addicts and their partners in recovery. The older approach is often referred to as the co-addict approach. This theory is derived from substance abuse treatment and it labels the betrayed partner as a co-addict. The idea is that the partner is somehow complicit in the sexual acting out of their partner through codependency and enabling. This approach has proven harmful to both betrayed partners and sex addicts because it amplifies the pain associated with infidelity.
The other, newer model, is referred to as betrayal trauma model. Unlike the Co-addict model, betrayal trauma focuses on the physical, emotional, and spiritual consequences that betrayed partners experience due to infidelity and sexual acting out. In session, addicts will often accuse their partners of being vindictive or trying to punish them. However, this can be better described through the lens of trauma than it can be through codependence. Counseling for betrayed partners should focus on normalizing the trauma response and working to rebuild trust in a relationship. I if you have been betrayed by your partner in infidelity you should ask your therapist or group which model they adhere to, whether it be co-addiction/ codependency or betrayal trauma.