How do you obtain CCTV footage from ASDA?

To understand this answer more fully - please read the discussion page:

The problem appears to be that the collision took place on private property and therefore the collision is a civil matter between the two parties involved. Being a civil matter, the police can't/won't become involved.

It seems that your friend's only option may be to retain an attorney who might file a request with the court that ASDA (whoever they are?) release the tape. Other than that there appears to be no other recourse open to her.