Just to pop in with another possibility for your mood swings. You say you are already on two anti-depressants. If I were you, I'd talk to your doctor and see if these need to be adjusted or something else tried.

Anti-depressants aren't a one size fits all kinda of medication. And, they don't work the same way all the time. Some times they "poop out" and lose their effectiveness after taking them for a period of time. I'm currently going through that right now with one of mine. But, there is a solution. Your doctor can help.

As for the extra stress you feel dealing with a younger supervisor with an attitude, writing does help. Too bad you don't work in an environment where you can take a walk for a break. But, you might be able to take a "mental break". Next time she gets under your skin, step away, breath slowly, and imagine yourself some place that always made you happy in the past. Think about this place. What were the sounds? What were the smells? How did it make you feel?

Don't let her invade your special place.