given that Margaret is consistent with a birth year of 1874 in the 1901 and 1911 census,,,and you say in your other post she has a brother John b 1871,,,then this COULD be her in 1891
1891 census 27, Cwmcelyn Road, Aberystruth, Blaina
EVANS, Dinah Head Widow F 43 1848 Rhymney, Glamorganshire
EVANS, John Son Single M 20 1871 Coal Miner Blaina, Monmouthshire
EVANS, Margaret Daughter F 17 1874 Blaina, Monmouthshire
EVANS, Martha Daughter F 15 1876 Blaina, Monmouthshire
EVANS, Rachel Daughter F 12 1879 Blaina, Monmouthshire
EVANS, Elizabeth Daughter F 8 1883 Blaina, Monmouthshire
PEMBER, Henry Lodger Single M 21 1870 Coal Miner Leominster, Herefordshire