I think this problem is more common than you think (types the psychologist on her phone). It’s quite possible she doesn’t know the extent of how addicted she is, or maybe she feels powerless to stop.
Pick a quiet time to have the discussion, and don’t be accusatory: “We haven’t gotten a lot of time to talk lately, and I feel disconnected. Sometimes it seems I’m just watching you on your smartphone, and it makes it hard to have a real conversation.”
If she’s not motivated to make changes, you’ve got to explore why that is. Does she not view it as a problem? Is she actually seeking to avoid connection? The deeper you get, the more you’ll know whether this is about that sleek, shiny gadget, or about your marriage.
You’re right. You don’t owe them an explanation. And to plan some big confrontation when your supervisor has been supportive seems like asking for it. If they’re trying to create drama, they’ll only be overjoyed by you giving them more of it.
That’s not to say that you need to take their mistreatment. If they’re creating a hostile workplace, it’s worth talking to your supervisor. And as for your interactions with them, clean the slate and take each new comment as it comes. Respond matter-of-factly in a way that highlights how inappropriate it is: “I’m confused by what you’re implying: I had some medical appointments that I used leave for” or just a blank, befuddled stare followed by a “Wow. What a thing to say.”