Berridge or Rist?

Trying to find my grandads mothers side of the family, before he died he had told me that his mums maiden name was Berridge and i had never really gone back further than that as i was more looking at the Wankling side of things but now i want to try and trace this side back a bit too, so it came as a bit of a suprise when i saw on FreeBMD that my grandad's mothers maiden name was Rist. Looking up the marriage gave a little confirmation that something had happend to make my g-grandmas use a different name or at least make my grandad belive it was Berridge and not Rist

Marriages Sep 1910
Rist     Florence B           Nottingham     7b    658     
Wankling     James           Nottingham     7b    658     

from find my past it looks like she died in 1959 aged 72

Name:     WANKLING, Florence B
Registration District:     Nottingham
County:      Nottinghamshire
Year of Registration:      1959
Quarter of Registration:      Apr-May-Jun
Age at death:      72
Volume No:      3C
Page No:      231

The 1911 census has Florence B Wankling and James Wankling living with James and Harriett Berridge with James marked as Son in Law with Florence B noted as born in peterborough, so it looks like Florence had either been born out of wedlock or perhaps Harriett had remarried.

The 1901 census has a Florence B Rist living with James and Harriett Berridge and listed as step daughter so that clears up that little mystery hopefully.

Freebmd also gives Florence Beatrice Rist born Jul-Aug-Sep 1887 in Peterborough

To confuse things again slightly the 1891 census has a Florence Rist born 1887 in Cuckfield, Sussex - Tracing this side of the family might be a bit more complicated than it first looked!