Like someone said, you can't really police who someone's told about magic. Technically you could probably tell anyone, the only scenario that would cause issues is if that muggle believed it and then started telling others or in some other way making trouble for wizards. So it comes down to being careful who you tell. If you're telling a member of your family you're probably not going to tell Puritan Great Aunt Alice but your supportive muggle cousin who wouldn't cause trouble would probably be fine.
As for doing magic in front of muggles, I think the members of your immediate muggle family are fine because they've been told about magic when the kid was given their hogwarts letter and the Ministry would know that those muggles are enlightened ones. If Bobby Muggleton told his extended family and also his friends and then started doing magic around them all the Ministry would probably turn up like hey what are you doing these are muggles and he might be like Oh it's fine I've told them they're chill and then they'd probably be like Uh dude that's 30 people, statute of secrecy man, it's obliviation time.
I think probably the only time you'd have a potential issue telling a significant other about magic (in the VE) is if you told them too early and you're not engaged yet and you use magic in front of them OR they're a blabbermouth and you didn't impress upon them how serious it is to keep it a secret. OR if it causes a break up and you don't obliviate them. I can't imagine they'd expect a divorced person to obliviate their muggle spouse because that would probably incredibly intricate if you've been together a while. They might leave them if they seem benign but I guess the Ministry could get involved and obliviate them if they think that muggle poses a threat.
Thanks to Bee for this magnificent set <3