Hi OP - I am late to this thread but just wanted to send hugs. My DD is also on lexpro and it has been beneficial. It took a few weeks and then of course there are still bad days, but increasingly the bad days are less than the good days.
I know the obvious of getting outdoors more and engaging in hobbies can be kind of hard to hear because it can be hard to get a child to do, of even if they do them, they're just going through the motions. So, I ask a random question - do you have a dog? If not and your DD is interested, it might be something to consider. It's a responsibility but also a joy, and it helps get people outside (walks, dog park, etc.) It also brings the benefit of caring for something else, something needing you. It also gives families/siblings a shared experience.
So, just a thought. You might already have one, in which case ignore. But it's something that can be very helpful in providing structure and purpose to the days.
Best of luck. Also, remember to savor the small victories, just like it seems you did today.