dzug is wrong. Section 150 of the Licensing Act 2003 says that only 16 year olds upwards can have alcohol with a table meal. Its unlawful for 15 year olds to be served.
There is also a difference between 16 year olds being sold alcohol, being deleivered alcohol and being given alcohol. It depends where and how it is done to determine who commits the offence.
Section 150 also makes it an offence for anyone under 18 to consume alcohol on licensed premises. �1000 fine, that should put her off.