I'd say they're worth a shot at the very least. But if your friend is seriously feeling down about the ending then I wouldn't rush into it, as you could definitely come out feeling even worse, considering how polarizing the Epilogues are.

I won't delve into specifics but I'd also like to add that the Epilogues aren't really the "conclusion" to Homestuck you might be looking for, it's its own beast entirely. It has way more adult themes and explicit topics explored, and just generally has a different "feel" to Homestuck that I can't adequately describe.