Hello belle: I see this is your first post here on PC. So... welcome to Psych Central. The relationships & communication forum, here on PC, may also be of interest to you. Here's a link:

https://psychcentralforums.com/relat...communication/

And then here are links to 3 articles, from Psych Central's archives, 2 in particular that discuss how to handle the types of situations you describe in your post:

When Your Adult Child is in a Bad Relationship

When You Don't Approve of Your Adult Child's Relationship

Take These Ten Steps Closer to Your Adult Child

I hope you find PC to be of benefit.