What should i do about my step daughter and her neglectful mother?

You are wrong in assuming that child services will not get involved. Neglect is neglect. While they may not be too worried about dirty clothing, bad hygiene is another story all together. Stop covering for this neglectful mother and call child protective services. - At some point, when this little girl starts school a teacher will notice and make the call... and then both mom and dad will be in hot water... her for neglect and him for not reporting it.