I thought you had to be 18 to get a tattoo in uk?

She must have either been tattooed while in another country or went to a tattoo artist who was prepared to risk breaking the law. It is not legal to be tattooed if you're under 18 in the UK even if your parents give their consent. Unfortunately, unless Cher is prepared to say who tattooed her, there isn't a lot the local authority (who enforce the laws regarding tattoo studios) can do.