I don't disagree at all. You are right about the part that some people are not able to pull themselves out of that phase.

I know there are some people for whom it's harder to recover. They dive in way too deep and harm themselves as a way to outlet their emotions, but that is a completely unhealthy way of experiencing sad emotions.

Your friend already seems to be dealing with depression. Oftentimes, people with depression are really good at hiding their feelings, and that's why they shut themselves out and into loneliness.

I can dive deep but still end up recovering rather quickly (not always) because I've taught myself how to do that and it feels so good to experience the beauty of sadness and still get back from it just as fast.

I don't think your friend should be doing those things to herself. It's toxic. If she can afford it, ask her to go see a therapist and talk to her about it more often.

I've been there, and it really helps to have someone who is listening to you and about your problems. I hope she gets better.