We are 2.5 years since DD's MH fell off a cliff at the start of the pandemic, around 2 years since she was at her worst, and 18 months since she started Fluoxetine.
It isn't a smooth climb back to health, there are lots of ups and downs. I have found that keeping a short one line record of mood / activity has helped me see improvements and helped give me hope. I don't do it all the time but when I do it helps see progress.
Your DD was able to be active last week, that's a good thing. Maybe she overdid it so has retreated this week. Maybe next week or the week after will be better.
My DD is due to college 4 days a week. Last year she managed 75% attendance. This year she hasn't yet done a full 4 days but hopefully we'll get there.
I forget which year your DD is? Is school providing any home tuition at all just to stay in contact.
Little steps: our little steps were things like:
bed all day -> up but in pjs -> up and dressed by lunch -> trip out in car in afternoon -> trip out including a short walk.
Even now at weekends during term time DD can't do much more than the last step, but now she asks to go rather than having to be persuaded.