Pity about the birth date, there's only the 1901 that she'd be on. Was she at that address when she married or was she born there? If her father was a farm servant, the family might have moved several times. Pretty sure she's not there in 1901. Nearest I can find is this
Dyrhyd, Mydrim RG13/5116 folio 65 pg 4
David Lewis head single 69 farmer b. Carms, Merthyr
Elizabeth dau 35 single b. Mydrim
Anne Mary Griffiths grand-dau 11
Sarah Ann Griffiths 10 grand-dau
both grand daughters born Llanfihangel Abercowin
Only Ann with place of birth St Clears, age doesn't match & she's Sarah Ann
Cottage, Laugharne RG13/5111 folio 64 pg 9
William John head mar 38 carter with grocer b. Laugharne
Mary wife 39 b. Laugharne
Sarah Ann dau 12 b. St Clears
Frederick son 7
Elizabeth Jane dau 3
all children born St Clears
best match for age, but not with parents
33 Curve St, Aberdare RG13/2037 folio 29 pg 9
Thomas Phillips head mar 53 coal hewer b. Pembs, Fishguard
Ada wife 50 b. Carmarthen
Benjamin John Phillips son 23 coal hewer
Elizabeth dau 21 dressmaker
Margaret Hannah dau 19 servant
William Henry son 17 coal hewer
Thomas son 16 coal hewer
Ann John visitor 9 b. Carmarthen
all born Aberdare except where stated. Think Ada's maiden name was Thomas, so no obvious relationship.
A possible born Llanelly, age out, no parents.
Penyfodau Ganol, Gowerton, Glam RG13/5086 folio 41 pg 73
David Morgan head widower 86 woollen weaver b. Glam, Llansamlet
Daniel son mar 56 coal miner hewer b. Glam, Loughor
Mary dau-in-law 44 b. Carms, Llandeilo
Ann John grand-dau 7 b. Llanelly
David J Morgan grand son 5 b. Loughor
If she was born in Mydrim, it's unlikely to say Llanelly on a census as they are not near. Sorry to sound like a broken record, but you need the marriage certificate for her father's name. You could end up following the wrong family if you don't get documents.