Hi Hilary:
The 1901 census was taken March 31. If your relation was born in April 1901 she would not have been there. Perhaps this is the family that you are looking for:
1901 England Census
RG13/3490
3 Bradfield Street
West Derby Lancashire
William Foley abt 1862 Born Preston, Lancashire, England Head, an Electrician
Hannah C Foley abt 1865 Born Preston, Lancashire, England Wife
Clarice E Foley abt 1887 Born Liverpool, Lancashire, England Daughter
Leslie G Foley abt 1890 Born Preston, Lancashire, England Daughter
Lillian D Foley abt 1896 Born Penwortham; Preston, Lancashire, England Daughter