If something happened to my best friend id be so sad not to be able to talk to them again.

if you had about a decade of chat logs, you could make a pretty good AI.
I'd assume its not difficult if you have all their messages in a text file, you could just tell the ai to form their personality around it off the jump and make it a permanent condition. AI can analyze text files these days... You would just need a local one ( ´ω`)