Aw no Kate, usually I'm knocking about at silly o clock too! So sorry on top of the stress of covid there's a breakdown in a friendship to process. Are you sure she's not being taken advantage of because she's vulnerable?
Donkeys years ago my sister was in a similar situation when she had a breakdown?
If she does need some help and support with her mental health, then she will kick back against it initially, if she's a good friend id step away but say you'll be there if she needs you.
I'd be tempted to tell the guy to back off too or risk his wife finding out...but that's just me
