OK - I don't believe that saying anything to your W about it is going to make a difference so I agree with S. If I remember you tried addressing your concerns to your W before about it and she responded by sending you pictures of S3 in bed at her moms or something like that. Obviously it did not change her behavior.
With that said if you have evidence of abuse, child endangerment, neglect, etc. speak with your L ASAP or if it is an emergency call the police.
Finally you really need to think about all the above or if this is just something that really really [censored] but as your S's mother it is within her right to do. The difference between your values and hers.
