I'm not sure where to post this, but I need help, and answers

Someone close to me has been relaying feelings like they have suddenly become depersonalized. They recently had a panic attack (for the first time in their life) about 10 days ago. Ever since then, complete anhedonia has set in. They sent me a screenshot of a thread they found that really relays how they feel, and I agree with it completely. I'm just really frightened and concerned. They went to see a doctor recently, too, to see if they could get their hormones checked (a physical, basically), etc. And the only thing that happened was that they received 25mg of Zoloft to treat depression. I personally don't know what to do. Everything was so sudden. This person was able to feel prior to the episode, but, now they feel absolutely nothing, and symptoms of depression are just completely evident now. They were perfectly fine before. I know this person like the back of my fucking hand and I just want to understand. I'll crosspost this to depression, but, I don't know how that would help. I'm just scared and really confused (though, not more than they are). If there were a mental illness subreddit, I'd post this there. This person is my rock and if someone can give me answers, please, I just beg of anyone for any help.