I don't want to repeat the debate, for sure. I was just amazed that she even asked.
Is there are UK law that bans headphones? If so, are you sure it written to allow these?Buy her a pair of Aftershokz bone conduction headphones. Ears are open to all other sounds and they are fabby. Legal to use on the road or when driving a car too.
Well, perhaps you should do if you want to talk about helmets and headphones(rarely go to headphone/helmet sub forum)
Always have and always will when riding solo.
Each to their own innit