Good luck.

It's always sad to see when a vanilla couple has problems because one partner goes off seeking bdsm outside of the relationship, especially when children are involved.

Sometimes it's indicative of a whole different set of issues (grass always greener kind of thing, 7 year itch etc) and sometimes the person started the relationship with a vanilla partner while taking a break from the bdsm lifestyle and then gets drawn back in.

Most people I know in the lifestyle in real life are very uncomfortable with the idea of cheating (which can vary from doing anything with someone outside the marriage or relationship to actual sexual contact) as it implies there are partners who do not "consent" to the arrangamnt what ever it may be cybersex only or otherwise becuase it goes against the basic tenets of safe, sane and "consensual".

The more honorable of these acquaintances would have already let her go or revoked contact with her once they found out she was married and you didn't approve.

It may be embarrassing but if you are already in consoling with her...bring these issues up with the therapist. A kink friendly therapist can be found if necessary a lot easier than one may at first think.