Hi - If you are looking for them in 1881 through Ancestry or FamilySearch, it might help to see how the Ancestry index lists them in 1891:
Name: Leah Leadbetter
Age: 13
Estimated birth year: abt 1878
Relation: Daughter
Father's Name: Reber
Mother's Name: Lech
Gender: Female
Where born: Douglas, Isle of Man, Isle of Man
Civil parish: Maughold
Ecclesiastical parish: St Paul
Town: Ramsey
County/Island: Isle of Man
Country: Isle of Man
Registration district: Isle of Man
Sub-registration district: D
ED, institution, or vessel: 3
Neighbors: View others on page
Household Members: Name Age
Reber Leadbetter 48
Lech Leadbetter 45
Cecles Leadbetter 17
Leah Leadbetter 13
Wm Leadbetter 11
Reber Leadbetter 6
Wes Leadbetter 3
Mary Leadbetter 0

Note that mother's name apparently given as Leah rather than Mary.
[Also two Leah Leadbetters in 1901 index Whitehaven, aged 49 and 23, with Thomas 13, Mary 10, and Charles P. 11 months.]

Sue