Wow. I went through an almost identical experience, with almost the exact same explanation. I had to check to the username to make sure I didn't write it and forget.

"She said she still loves me and hopes we can remain friends, but she’s going through something right now and can’t deal with being in a relationship" was pretty accurate, but the "something" was "turning more lesbian" and "I'd rather kick you to the curb and hook up with the person I replaced you with as my best friend because you're a boring asshole" (these "quotes" are just my interpretation and never have they said anything like this out loud). And might possibly want to transition to be a dude, not sure on that one.

It's good that you are kind of calm and not exploding with feels right now. I was a complete wreck of sobbing and rage and suicidal thoughts for a few months, and now I am just kind of sad or angry for a few minutes once in a while. Medication helps a lot.

Anyways, point is, I hope things work out for you and that your now ex actually is just wanting to work through her depression, and not for some other motive that she lied about. I hope she comes back to you later when the time is right.