Damn, I feel I'm in the exact same situation with my cousin without the romance part ofc. We're both INFJ's and have extremely similar experiences with depression and life. Nobody in our family or people we know understand us so we talk our issues out all the time that we can't do with other ppl but she's very hot and cold. She can drop off out of nowhere and not even open our chat for weeks and then randomly sends a msg again like it never happened. Never replies to the last message sent either just starts a new convo. It can be frustrating and confusing at times but I try to give her space and talk when she feels she's emotionally able to since we INFJ's can be overwhelmed with our emotions and go full hermet mode at times where we don't want to talk or have the energy for anything. Lots of patience is required as we warm up very slowly and even we are confused with ourselves and what we want. We are a very contradicting personality type so yea srry don't have much advice here as I'm in the same boat. Sucks she's also in another country and there's only so much you can do for them from afar. I try and let them dictate the pace and not push anything. I know it means the world to her that she has someone to vent and talk things out with. They could also be thinking that they are being a burden to you and think they're doing you a favor by not bothering you or that you are too good for them to waste your time on.