Hi Sarah I have transcribed all the kerfoot births since registration began in 1837 up to 1932. There are two Isabella's registered in Lanashire 1) born in the March quarter of 1947 Registered at Bolton. The reference to obtain certificate is (XX1 132) 2) born in the Dec quarter of 1869 registered in Preston. The ref is (8e 570)
I have also recorded Marriages up to 1950 and possible entries are as follows:- March quarter 1892 Preston, and June quarter 1898 Salford.
As Rufford is not far from Preston that may be your best bet.