If we have got the right girl ,then she is still unmarried by 1891
Dad Isaac dies:
Jan/Feb/Mar 1899
Isaac Catlow age 82
Burnley 8e 138
would be interesting to see if MAry is the informant on the death cert and if she is still Mary Catlow then, or Mrs X
Cant see Mary, or her mum as widow in 1901. Mum may have died too by then.
(modified to add - there are 2 possible deaths for Mary, the mum, in 1894 - likely one of these is her. So if she died first, and Mary the dtr was close to them as was still at home for the longest, then it could well be that she would be the informant on dads cert in 1899. well, maybe!)