I am really sorry to hear about all of this
I dont think i can say something smart here. But depression is hard, its something that almost all people on this site have been or are going through. It causes a big toll on persons mind, but that "old" person, person before depression is still there, just trapped in veil of some strange unexplainable darkness. Emotional cheating is a bit odd i guess... I mean its hard to separate romantic feelings from friendly feelings. What differs them is sexual attraction and level of intimacy and general connection between 2 people. But if she loves you she should try to be supportive and nice and everything towards you. To help you feel better and not to go around seeking for possible affair.
But even though it happened what happened, i do think that every relationship can be fixed with decent effort from both sides. We live in age where stuff that get broken are tossed away without trying to fix it before tossing it away, similar thing is happening to relationships. Maybe relationship counseiling would be good for you two?
I wish you very best, keep your heart safe. Work on getting better. You will getter