Let your friend know that you’ll be there if she needs you. The guy does sound like he’s abusive in some ways and a big part of that is isolation. If all the friends and family are driven away, there is no one to help if they want to escape. So let her know “I’m always here. If you need me, call, text, send a carrier pigeon. I’m here.” I know more than one woman who was able to escape a domestic violence relationship because one of the friends that was driven away, came when they called.