MN1 Form with consent from only 1 parent

Hello,

My daughter is 17 and applying for British Citizenship via the "Apply for registration of a child under 18 as a British citizen" route.

She has been living with me (her dad) for the last 7 years and never spends any time with her mother. She also doesn't want her mother to be involved in this.

In the application, there is a section about Parent or Legal Guardian Details. Does her mother name have to be entered there or can we decide to not provide it?

On the MN1 form, there is a section which states:
"If only one parent has signed, please say why the other parent has not signed and provide supporting documents"

What kind of evidence would be acceptable?

Thanks

Are you legally separated or divorced from the mother? Is there a child custody agreement/court order? All of these can be submitted as proof of sole responsibility.