It's curious because her parents married in 1871 and had no other children which I find a bit unusual.
It seems they did have another child, born and died in the same quarter in 1875.
Births Mar 1875 BRIGGS, Edith Matilda, St. Olave, 1d 217
Deaths Mar 1875 BRIGGS, Edith Matilda, Age 0, St. Olave, 1d 173
GRO index has the mother's maiden name as ROFFEY
No luck as yet with Birdie - still looking.