The great majority of Shirley's alive at the time seem to have had a middle initial (usually A). If we assume that your aunt did not have any middle name and look for marriages between the ages of 16-40 we get possible married names of:
HEATH (Southwark, Q4 1957 - unlikely)
MARSHALL (Goole, Q3 1960)
CHANDLER (Barnsley, Q2 1966)
ANDERSON (Barton, Q1 1974)
BOARDMAN (Rochdale, Q2 1977)
*CROOK (Halifax, Q3 1973)
*This is the only Fearnley one, all the others are Clements.
So you could try focusing on those married names but there's no guarantee that she's included.