She shouldn't be allowed to deny this request. Oh but her human rights and dignity
The law applies to everyone equally. The specifics of what this woman has alleged to have done are neither here nor there. If you are contending that the police should have the right to force compliance in this case, then you are also contending that they should have the right to force that upon anyone arrested for any reason whatsoever.
What exactly is it about people having human rights and treated with dignity that you object to?
Do you not recall what used to happen when the police were given carte blanche to deal with suspects as they saw fit?
The idea that people should be considered guilty as soon as they are placed under arrest appears to be a fairly widely held one on Mumsnet, and I'm sorry, but that is completely barking mad.