I don't see where all this BS about her being an unfit mother comes from when we don''t even know either the family or personal circumstances of these people.
Scenario:
Two separate families have similar circumstances; the parents are separated and the father has custody of all the daughters. Recently, the oldest daughters in each family have finally confided to their mothers that her fathers been sexually abusing them for many years, and are now turning their interests towards the next oldest daughters.
In Family "A" both the mother and the oldest daughter are afraid that the pattern will continue with the younger daughter, so they formulate a and execute a plan to get all the daughters away from the father and to safety in another country.
In Family "B". the mother tells the daughter she is a liar, and she carries on in denial of what she can see has been happening right in front of her for many years.
Who's the unfit mother now, A or B?
Now I'm not saying that this is what is happening with THIS family, but it is one of a number of possible scenarios that fits the picture, especially with the two oldest daughters being the most upset about having to go back to their father.