Growing up in a small town, I had one friend throughout my school years - we shared interests outside of the norm as well as certain difficult aspects of our family life, and even after we parted ways for further education (her going to a different country, across water) we somewhat kept in touch. That is to say, we didn't exchange messages much at all, but any time she was home (summer holidays and over Christmas most notably) we would meet and catch up.
During this time, a year after we finished school, she told me that she was diagnosed with a condition. To my knowledge, it is mostly incurable but is treatable, and can cause depression and low energy. I can't say for sure if this actually has any importance but I feel it might.
Cut to 3 years after school - I graduated, and my friend was repeating her third year of university, with two still to go. My final year of university really took it out of me, having struggled with social anxiety and depression, which to this day are still an issue for me. I happened upon a job opportunity that would involve me relocating to the city my friend was studying in. I swiftly let her know it was an opportunity via text, and she seemed as enthusiastic as I was.
The weekend I moved, we met up. Regrettably, I arrived an hour late to our rendezvous, and I worry that rubbed her the wrong way; additionally, I think the meeting ended on something of a sad note. I may be remembering it worse than it is, but I definitely came away from the meeting feeling quite morose.
We haven't met since then, which is nearly a year ago now. Depression hit once again, and only exacerbated my inability to initiate conversations. As such, the messages we exchanged were extremely sparse - maybe one "How are you doing?" a month, which either went ignored on her end, or led to a few basic texts catching up, maybe once a season.
This didn't strike me as an issue until recently, when she indicated she'd like to meet up at the end of August in a text at the end of June. When the end of August came, I texted with another "How's it going?" and got no reply. Around a week later (a week ago now, start of September) I followed up saying that I hoped she was okay and that I'd love to meet up with her when she was free, and again heard nothing.
In general, I've not been very popular, or good at making friends, so I treasure the ones I do have - I may just not be very good at showing it, due to my insecurities. She's one of the few genuine friends I've ever connected with, that felt more than just a "friendship of convenience" as I've become accustomed to.
Is there anything more I can say/do to try to re-engage her? Or is this her way of cutting herself off from me, having found better friends? It's the living in limbo that's really hurting me - if I knew I could process and start to recover, but for now I'm clueless and hopeful. I've been considering actually calling her instead to more proactively engage her, but it's out of the ordinary for me, and I'd worry that it'd be rude to do it without warning like that.
Sorry for the wall of text, but I wanted to give as much detail as possible! Am new here as well, so if I've done anything wrong, please let me know.
TL;DR - With depression as a possible factor on both sides, and after having texted occasionally with little response, how do I proactively rekindle a waning friendship?