Overriding screen time by changing the time settings

I have set my teenage daughter’s phone to block at bedtime but she is overriding this. Initially I thought she was extending screen time but this isn’t an option as I’ve set it up correctly with a passcode. I’ve come to realise that she is going into the settings and manually changing the time on her iPhone. This then knocks off the blocks I’ve put in place, is there anyway around this? Thanks