Four years, four months. Aside from treading water on your PhD, do as your therapist suggests and focus on “do[ing] things you like” these next three or four months. If you don’t know how already, learn how to cook a few of your favorite meals. You don’t sound like you have the #1 problem/cause of “rock bottoming” (alcohol use disorders), but you might want to avoid alcohol-focused interests right now.
On the flip side, at least she bailed before the marriage, mortgage, and kids. She’s broken your heart, but she's hasn’t ruined your financial future. That sounds a bit cold, but might be a non-negative thing to remind yourself of when you start dwelling on her.
(Edited to add) My husband met me when he was 32, about a year after he’d finished his PhD, taken a couple of months to find a job, and moved across Germany for said job. It doesn’t feel that way right now, but you’ve got time.