macOS supports multiple users beautifully; I've long done that with my family of four. Everyone's stuff is kept separate and organized the way they like.
At least one user must be an "admin" user, the rest can be "standard" users. One thing to know is that an admin user can, with some effort and technical knowledge, see and open the files owned by other users. So that's a possibility to keep in mind regarding privacy. But in everyday, normal use, no one would see others' stuff.
Of course, only one person can use the display and keyboard at a time. However, you can use "Fast User Switching" to leave user A logged in while (relatively) quickly switching over to user B. And then you can switch back to A, etc.
EDIT: I'd recommend each of you have their own Apple ID. Your Mac account would be signed into your Apple ID, and her Mac account to hers.