Okay so basically my gf convinced me to play this game and i love it. i plan on buying a switch and a membership and the game to play. we set up an account on her switch so i could play it doesn’t have a membership but it’s connect to the email i liked to make my account with. i’ve started playing in her island i have a house and yadayada. basically what i need to know is when i get my switch and everything else will i be able to use my account with the email and transfer stuff with a new island but same character and inventory or will i have to restart and create a new island or what will happen? i want to use the same email is that even possible at this point? what will happen to my house in her island?
If you get your own switch and start a new island, you'll have to make a new player and house. However, you can leave the stuff you want to carry over on the old island (only includes items you can drop on the ground outside, not place. Placed items can't be picked up by visitors, and they can't be dropped off by the original person), and then go back and retrieve it when you're able to later.
About using the same account on two different consoles, you may have to go to the Nintendo Support forum and ask there (or find a thread where someone else already asked). I'm not sure how that works.
EDIT: If you're planning on buying your own online membership then it would be best to just create a new Nintendo account. You can potentially look into the online membership's family plan, that might have what you're looking for. I've never bothered with anything beyond just buying the membership for one account and one console.