You are right. On several Australian certs she is listed as Louisa Stemp.
We think this is the same Louisa in the 1881 England census...14 years old now compared to 4 years old in 1871:
Name: Louisa Stamp
Age: 14
Estimated Birth Year: abt 1867
Relationship to Head: Servant
Gender: Female
Where born: Middlesex, England
Civil Parish: St Pancras
County/Island: London
Country: England
Street Address: 48 Hampden St
Education:
Employment status:
.
Occupation: Servant
Registration District: Pancras
Sub registration district: Somers Town
ED, institution, or vessel: 12b
Neighbors: View others on page
Piece: 202
Folio: 76
Page Number: 32
Household Members:
Name Age
James Stone 36
Harriett Stone 36
Willie Stone 11
Minnie Stone 3
Reginald Stone 1
Louisa Stamp 14
Working as a 14 year old servant for the Stone family in St Pancras, London. We couldn't find any death or marriage records for this Louisa, and she doesn't show up in any other England censuses. So we're going with this one

3 years after this census, age 17, she hopped a ship to Australia for a new life. It would be really nice to know for sure though.

Thank you very much for your input!
Cheers,
Rob.