The minimum possible amount of time
This might sound strange or harsh at first, but hear me out here...
Removing an answer not fit for the site quickly will A. Protect that answer from receiving more downvotes and B. Protect the asker (or others reading it) from trying to use that unproven advice.
Let's take your deleted answer for example. You recommend trying to connect the friend with a therapist or support structure. To my ear, that doesn't sound like a bad idea at all. But that's the thing, I have no experience trying to recommend a therapist to a friend. For all I know, this could absolutely backfire and make the friend extremely upset. Or a therapist might be the wrong choice. You give no arguments and no evidence that things will work out nicely the way you say they will. (To be clear, I'm not saying they won't. Again, this sounds like a good suggestion to me, but lacking experience myself, I can't say).
Once youyour answer has been removed, you're free to edit it as you please. For answers that can be fixed (like yours), I view deletion as a kind of staging grounds where you get to work on things behind the scenes before undeleting.
Once you feel the answer is up to spec, you can A. flag the answer as custom and leave a message for the moderators letting them know you think it's in a state to be undeleted. B. Hop into chat with us and mention you've fixed up a deleted answer and you want some eyes/opinions on it. Or C. You can write a meta post for clarification if you feel nothing's been done.
To reiterate here, deletion doesn't mean your answer is dead. It only means that now you get to work on it in secret so that it can make a second debut :) And I think the quicker we delete an unfit answer and toss it back to the answerer to fix, the better. If we don't think an answer is fit for the site, we don't want it to be getting more views.