Help with alt accounts

Hello! I have sent a message on SFA about this and reached out to a few moderators, so sorry if I'm being annoying about this. I was wondering if it was allowed to create an alt account if it's being run by a different person? My sister wants to join the game, but unfortunately we only have one device to play on. I read through the rules and there wasn't much on this scenario, so I was wondering if a moderator or someone else knowledgeable could help me here. Thank you!

It's been discussed before, and there are a few players on here with multiple accounts with different people, e.g, @GamerGuy and @DiamondStone, @YoshiFromWiiCube (me ofc) and @ShortBug-The-Gamer, and some more I can't think about at the moment...

Edit: Wait, sorry for jumpin' in...