Heather Ilott will get £164,000 after initially being left nothing by her mother Melita Jackson, who died in July 2004 at the age of 70.
Mrs Jackson wanted her estate of £486,000 to be split between The Blue Cross, the Royal Society for the Protection of Birds and the Royal Society for the Prevention of Cruelty to Animals.
Mrs Ilott, who is an only child, had become estranged from her mother
for 26 years and the court heard several attempts at a reconciliation
had failed.
The appeal judges ruled in her favour, stating that her income was "not reasonable" for her future as she was on benefits and had no pension.
They added that Mrs Jackson had "no connection" with the animal charities.
Mrs Ilott was awarded £143,000 to buy her rented home from a housing association, and an extra £20,000 as "additional income".
Experts have said the decision could leave wills open to challenge.
Gary Rycroft, a member of the Law Society's wills and equity committee, said: "This ruling is saying that while you can still disinherit your children, you are going to have to explain why and show connections with those you are leaving the money to.
He told The Daily Telegraph: "It is also very important because it seems to be making it easier for adult children to claim for reasonable financial provision in wills and has made the gap wider for them to do that."
Mrs Jackson became estranged from her daughter in 1978 when, aged 17, Mrs Ilott left home to live with her soon-to-be husband Nicholas Ilott.
The couple have five children and live in Great Munden, near Ware, Hertfordshire. The judges said they earn "very small incomes" and their monthly expenses were "modest".
In a judgment handed down on Monday, Lady Justice Arden said: "This is a case where the court can and should make reasonable financial provision out of the deceased's estate for the appellant's maintenance so that her living expenses are relieved without affecting the state benefits on which she relies."
The appeal judges ruled in her favour, stating that her income was "not reasonable" for her future as she was on benefits and had no pension.
They added that Mrs Jackson had "no connection" with the animal charities.
Mrs Ilott was awarded £143,000 to buy her rented home from a housing association, and an extra £20,000 as "additional income".
Experts have said the decision could leave wills open to challenge.
Gary Rycroft, a member of the Law Society's wills and equity committee, said: "This ruling is saying that while you can still disinherit your children, you are going to have to explain why and show connections with those you are leaving the money to.
He told The Daily Telegraph: "It is also very important because it seems to be making it easier for adult children to claim for reasonable financial provision in wills and has made the gap wider for them to do that."
Mrs Jackson became estranged from her daughter in 1978 when, aged 17, Mrs Ilott left home to live with her soon-to-be husband Nicholas Ilott.
The couple have five children and live in Great Munden, near Ware, Hertfordshire. The judges said they earn "very small incomes" and their monthly expenses were "modest".
In a judgment handed down on Monday, Lady Justice Arden said: "This is a case where the court can and should make reasonable financial provision out of the deceased's estate for the appellant's maintenance so that her living expenses are relieved without affecting the state benefits on which she relies."
