1851 has two possibles
A 10 yr old Harriett bn Pinlico, living in Westminstrer, her Dad John is a pianoforte maker
A 6 yr old HArriet bn Tottenham, living Tottenham, her Dad John is a shoemaker.
Did you get her father's name from her marriage cert? If so what occupation did it give for him) and what address was she married from?