There is the additional problem of "Island Representative" . Whomever logs on first and creates the island is permanently the main character or "Island Rep" and the only character that can move plot along/buy major upgrades, invite new NPC villagers, etc. If that person stops putting time in (on your console), you have to play as them when something important needs to happen.
Alternatively, you can erase HerIsland and start fresh before y'all progress too far. Allow her to play a 2ndary character on your new island while waiting for her console to arrive. FYI, the town folk will mention/gossip about the character a lot make it someone you want to hear about forever/play yourself. Down the line, a 2nd character will give you more storage as you upgrade the 2ndary tent into a house with lots of storage... But while waiting, she should focus on mining resources, including Nook miles to take to her permanent island when her new console arrives.
Another option: If you keep playing HerIsland and do the Nuke after the new Switch arrives, then you can ferry over pocket full, by pocket full of bells, flowers, fruit, saved (unlearned) DIY cards, etc to start her out, and then ferry half of them back to yourself after you nuke and restart. You can move up this timeline if you involve a 3rd party, namely a trustworthy ACNH friend willing to hold all your stuff for a few hours/a day (I hope there aren't many full grown flowers/trees) during the nuke and restart process.
I have never done this. I'd guess DIYs likely get lost permanently. I don't know if things like Nook Miles get nuked too. ...The internet says: Oooh. Yes 100% of the data is erased when rebooting including all characters created (and their data). Total clean slate, like you just bought AcNh. Cash out those NookMiles into NM tickets and export them to another island before you erase the game's data.