Request for Termination due to Immorality

Good day.
I would like to seek legal advice. My husband is currently staying with a mistress. I kept my contact number from my husband but eventually he has known it. Now he is trying to keep the communications open. However, this mistress is so strict with my husband she doesn't even know that the cellphone is still functional (she threw it during one of their fights).
Now, I have this feeling that if she will know that my husband is still communicating with me she will bug me with her unreasonable text messages. (It's one of the reasons why I changed my number and keep it from my husband).
I want to stand for who I am now - the legal wife.
If she will bug me again I wish to send a letter to their HR Department to have their employee discipline before I proceed to a legal step.
Is it possible. Will their HR acknowledge it.
Please note that my husband has no employment. Only the girl is working.
Hoping for an explicit advice.

Thanks

the company is not obligated to do anything about it unless they have a strict policy on morality.

If I wish to file a legal case against her, what case should I file and what evidences should I gather?

As much as possible I don't want her to lose her job, but I wanted to put an end to her domination with us. Kindly advise. Thanks.