It was 12 that is true, however, in 1889 any marriage of a person under 21 had to have parental consent, this is why on many marriage entries the term 'of full age' is written in the age at marriage column, meaning they were 21 or above and legally did not need parental consent. It did happen that marriages took place where the bride or groom was under 21 but they had parental consent, it also happened where a bride or groom was under 21 but lied about their age and did not appear to need parental consent. In 1889, there was a huge increase in civil marriages or register office marriages due to the decline in church attendance, but also marriages of immigrants to this country who were not necessarily of an age they claimed to be.
Basically, if a girl's father gave her away and she was under 21, that was deemed to be the legal consent.