I and my daughter's mother are divorced. I purchased my daughter's iphone and set parental controls. I am ok adding my ex as an"adult" onto the phone but I don't want her changing my settings. What is benefit of adding her to the family unit?

I have set up parental controls for my daughter's iphone. My ex would like to be added as an adult to the parental controls/family unit however (1) I don't want her to change my settings and (2) I'm unsure of what benefit there is in adding her since I don't want her to change settings anyway. Is there some purpose gained by having her as an adult member? I'm not opposed to it as long as possible to prevent her from changing my controls (Of note, if there IS a way to have her control/security options active when she has her and mine when I have her, that would be fine. I'm not opposed to her setting her preferences but don't want to get into a battle over this.

thank you for your help!