Please try to stop feeling ashamed of your daughter's behaviour, However hard you try to conceal it, those feelings will show and quite honestly how three adults chose to live their lives is not your business.
I understand why you feel that this is a situation that could well hurt the children involved, but whether they are hurt or not depends largely on how the adults involved act.
Your son in law was presumably well aware of what was going on if both you and your other daughters had seen the truth.
Now your daughter has told you in confidence what the situation is.
You didn't say why she felt she should confide in you. Did she want to discuss things, or was she asking for help, or did she just not want to lie by inference to you?
Please try to accept that your daughter has made choices that you would never have made, but that she is your daughter and presumably you love each other, otherwise she would not have confided in you.
We don't have to like or approve of the way our adult children live their lives, but we do need to accept their right to make their own choices and to do or try to do whatever makes them happy.
Shall we reboot our cartoons thread again? 😁
Talk to me about Dog Walkers (please! 😊)
from someone who estranged from daughters for more than 20 years