Sorry to disagree!! but I cant see any evidence that she is their daughter! She is with Edith in 1901, both as boarders in the same house, but she could be Edith's cousin, for example.
Obviously it is entirely up to you, but I wouldnt want to say who her parents were without the cert or some other evidence. Just a shame we cant get the family in 1891 all together. Or even all apart for that matter!