What would you say are better things to do for rest and recovery than screens? I totally agree that walking in nature really helps, but it's not always logistically easy.
Depression is a whole different situation, and I don't know enough to comment on it... but I imagine that a relatively healthy person is not getting nearly enough rest needed to cope with our overwhelming world. I think we all underestimate how important sleep is and how to get a really good night's sleep (something I'm totally struggling with).
Basically, I don't know your friend, I don't know anything about her, but I'm happy to give her the benefit of the doubt that her not getting to the gym is more likely for reasons of exhaustion than laziness.