I’m having a hard time understanding why you need all of that to just log into your jellyfin when you’re not home! You don’t need wireguard. That is something you chose to do for some reason. I can do it with literally the same way you said it

“install the plex app and i emailed you your login details.”

Replace plex with jellyfin. Your mother won’t need to do anything but downloading the app and putting in the credentials. Get a domain from cloudflare for $10 a year and set it up on the server. That’s it. No need for wireguard. I did the same thing for my friend who uses my jellyfin. I only sent him username and password. That’s it.