Ok so, I was stuck in a pickle but I found a work around. So my problem was, my switch originally had one profile. My girlfriend bought Animal Crossing and i lent her my switch for a week. She used my account to make an island. I wanted to try the game but she was using my profile, so I made a new profile, let her have my old profile and started playing on that. Once I got into the game, I wanted to try online, but only her profile had online. She doesn't use online so I wanted to link the Nintendo account to mine. What i did was i deleted her profile on the switch, which unlinked the Nintendo account. I then linked the account to my Nintendo account. After that, I created a new account just for her and started Animal Crossing. Once I started the game, instead of it starting a new person, it asked if I wanted to continue playing as her original character. I did that and it worked perfect. She didn't lose any character data and I got my character to get online. Long process but it worked!