Can’t change Admin to Standard

I could finally do it!!! I shut down the computer and restarted with my Admin Account. Apparently this is the only way to ensure the other account was logged off completely. Now it allowed me to do all the changes!

I already did that, but the other Admin appears in gray and it doesn't allow me to enter or uncheck anything. I also went through Login Options --> Join --> Open Directory Utility --> Directory Editor, but then it only gives me the option to delete the other Admin. I don't want to delete her (my daughter), I just want to change her from Admin to Standard.

Yes, I unlocked the Users & Groups pane, from my Admin Account, but my daughter's account (currently as Admin) shows up in gray. If I unlock the pane from her Admin Account and using her password, then I can get into her account, but I can't unckeck the "Allow user to administer this computer" because it is gray.