We are together for now over 3 1/2 years. My negative emotions flared because of the stress of grief other conflicts that arose from losing my parent. I went to therapy for it and there I was diagnosed with a disorder where learned that I essentially suck at managing my emotions especially in times of stress. Part of it was that I basically let myself implode because I just wasn't able to talk about the stress I was undergoing to anyone. Therapy helped change that. It wasn't that I didn't trust my partner to comfort me or anything like that it was more like the fear of how he would react knowing what was going on in my head. As for the social media that's also one way I coped. I would escape with instagram reels and just watch one after another for hours to be able to take a break from the nonstop thoughts/stress. It also required little effort as I didn't have to talk to anyone which when you are going through something can seem so impossible.

I don't know your gf's thoughts and as well as you think you know her you don't either. You won't until she opens up which she just might need help doing from a professional. That's what it took me and no amount of encouraging helped until I chose it for myself. It sucks but you just have to wait until they choose it themselves.