That's not possible. The driver for the phone isn't able to delete dashboards.
Do you mean, you want to give her access to receive notifications but not to access dashboards? That isn't possible. I would suggest that you use another means of sending her notifications if you don't want her to have access to other aspects of the hub. But if you did want to give her access, she would have to go to portal.hubitat.com and register her email address. Then you can go into your hub and add her as an allowed user. She would then use her credentials to log into the mobile app the same way you did.
How can you do that? You can't assign dashboard by user because dashboard don't require you to log in. You can create a dashboard and give her the pin but that means she would have to enter the pin every time she launched the dashboard.
If you don't trust her enough to give her the password to your home automation, then you haven't been with her long enough. Save yourself the trouble and wait. Create a tablet in the house for her to use with a dashboard.