Thanks, everyone, for your insightful words. They've been a great help.

In the end, it's just totally jarring and a little shellshocking to go from lots of communication, contact and plan making to a sudden illness, a diagnosis, then "see ya!" -- I don't think I'll ever completely understand, but I don't think it matters whether I do understand or not at this point anyway.

I agree that when it came down to it (and maybe before, I don't think I'll ever know) she wasn't invested enough to go through this with me and that's all that's really important in this situation to help me move on. Thank you, everyone, for helping me to see this with more clarity -- and for reminding me of a couple books I haven't read in years that I really should have a look at again

Thanks once again, everyone, for responding so carefully and thoughtfully!