The GRO index shows Jupiter John May [what a wonderful name!] marrying in Cambridge in 1853 with Elizabeth Cook on the same page. He doesn't appear with Elizabeth in 1861 or 1871, although she says she is married.
In 1851 a 13 year old girl named Louisa Leader is shown as a visitor to the Cook family. She was born in Stamford, Lincolnshire, and there is a birth of Louisa Leader in Stamford district shown on the GRO index for 1837. I can't see her in 1841.
Louisa Cook, daughter of Elizabeth May in 1861 is 23, but her birthplace is named as Barnham, Kent. (There doesn't seem to be a place called Barnham in Kent, but there is a Barham near Canterbury).
In 1871 33 year old Louisa is still with Elizabeth May, but now married to Joseph McCormick (marriage in Cambridge district 1869) - and her birthplace is Stamford, Lincolnshire.