I don't think any medical professional will give these girls the vaccine without consent on the day. It certainly doesn't tally with my experiences of consent. Nor would I agree with forcing a vaccine on a non-consenting 15 year old.
The girls are going to have to make a decision - if they continue to withold consent, their mother is going to wind up in contempt of court for not following the court order, isn't she? They need to weigh up the consequences of willfully ignoring a court order, which could potentially be very serious, against saying 'yes, give me the jab' to the GP/nurse/other HCP
I think the girls might simply agree to get the jab to avoid consequences