Hi There,
Is this your Marsh Family in 1851
43 Broom Street, Ince, Wigan.
Ellen Marsh H Wid 48 Weaver Cotton, Wigan
Jospeh Marsh son un 16 ass coal lab Wigan
Elizabeth Marsh dau un 14 cotton lab, Wigan
Ellen Marsh dau un 12 scholar, Wigan
Mary Rowbottam lodger wid 89, unemployed, Ormskirk
There are two Ellen Marsh's born in Wigan one in Jun 1838 the other Jun 1840 here are the BMD references for you
Ellen Marsh Jun 1838 Wigan Vol 21 page 757
or
Ellen Marsh Jun 1840 Wigan Vol 21 page 808
It might be worth trying to get one of these certificates stating Ellen as the mother and you'll have a better idea as to whether the mother had remarried or not.
Hope this bit helps any way
All the best
Tammy