Hey Philipp,
I had a somewhat similar situation with my daily use laptop. I really wanted to get away from windows but I use quicken to manage my bank accounts and credit card accounts. Quicken does not have a Linux version yet. (one day, I hope..) anyway, I had already switched my old HP desktop to Ubuntu, an older laptop to Zorin 17 and my wife's laptop to Zorin 17. All 3 were not compatible with windows 11. I finally decided to switch my daily use laptop to Zorin 18 last weekend. (yikes!) I created a backup image of my laptop, copied some important files to Dropbox took a breath and installed Zorin 18 directly to my hard drive. Worked beautifully. I then installed the virtual machine manager (QEMU/KVM). I then installed a bare bones windows 10 image in the virtual machine, downloaded/installed the quicken app in windows 10 and then downloaded my quicken data file from Dropbox. Cranked it up and everything worked perfectly. Now I use Zorin all day and when I want to run the quicken app I fire up the virtual session and do what I need to do.
If this is a brand new PC then you need to load all your data files anyway.
I assume (I know, I know) that if your wife doesn't have a Microsoft account she hasn't done a lot in windows already. Let her spend her learning time learning Linux/Zorin.
Just do some research on installing the virtual machine manager and windows OS within , there are a ton of YouTube videos available.
Lots of luck!