Hey again,
I understand now, sorry about that! The iCloud account would have to be logged in on both devices, but I wouldn't recommend this. If both of you are looking to use ALL the features of iCloud, your personal information such as Contacts, Calendars , Photos, and more will be merged together. I would recommend setting up two iCloud accounts and adding her to your family to share purchases and billing information.
Check out Set up Family Sharing - Apple Support. This is better than sharing an iCloud account in my opinion.
Good luck!