This is Samuel and I will discuss this and provide you information in this regard
I suggest you have a few things in your favor here and I am not sure why the DA or the police will not help you.
1 - It is a misdemeanor crime for anyone to entice a minor to leave their home. And it can be charged against the two sisters. You can read the law under CA
272. (a) (1) Every person who commits any act or omits the
performance of any duty, which act or omission causes or tends to
cause or encourage any person under the age of 18 years to come
within the provisions of Section 300, 601, or 602 of the Welfare and
Institutions Code or which act or omission contributes thereto, or
any person who, by any act or omission, or by threats, commands, or
persuasion, induces or endeavors to induce any person under the age
of 18 years or any ward or dependent child of the juvenile court
fail or refuse to conform to a lawful order of the juvenile court, or
to do or to perform any act or to follow any course of conduct or to
so live as would cause or manifestly tend to cause that person to
become or to remain a person within the provisions of Section 300,
601, or 602 of the Welfare and Institutions Code, is guilty of a
misdemeanor and upon conviction thereof shall be punished by a fine
not exceeding two thousand five hundred dollars ($2,500), or by
imprisonment in the county jail for not more than one year, or by
both fine and imprisonment in a county jail, or may be released on
probation for a period not exceeding five years.
(2) For purposes of this subdivision, a parent or legal guardian
to any person under the age of 18 years shall have the duty to
exercise reasonable care, supervision, protection, and control over
their minor child.
2 - You can certainly file for a restraining order
against the others/sisters on behalf of your minor child. You will need to state that the fact they have in essence kidnapped your minor daughter is in and of itself detrimental to the heath, safety and well being of the minor child. You should be able to fill out a statement of charges in the local courts - magistrate/district court to have the protective order issued. If that is granted, then the police must go get your daughter and return her to you. There will be a hearing where the sisters will need to appear and Show Cause as to why the order should not be made permanent against them
Again, I am not sure why the DA nor the police do not want to assist you with this. I suggest, you can contact the DA again and recite the above law and ask why that is not pertinent. That you are concerned for the safety and well being of your daughter and should anything happen to her it would be a basis for a lawsuit against them because you have been seeking help.