*hugs*
I'm not sure about this either. I've had my own experiences with shutting down, and sometimes it's hard to address because addressing it or talking to the person could make you shut down.
It would be a good idea to check in with this person like @Being of Cacophony said. If that's too stressful, maybe message them online or something to avoid a direct confrontation. If you can't manage either of those, try talking to someone else who you trust about it, it can really help to express it to someone and talk it through. I'm sure plenty of people, including myself, would be glad to listen on here, although it could really help to talk to someone in person.
Take care of yourself, you'll get through this.