but she is severely bi-polar and manic depresive can this help her and how?
Possibly; in order for a statement to be admissible it must not be made under any threat of punishment or hope of benefit, and if the person is under arrest and being questioned, then the person must make a knowing and voluntary waiver of their Miranda rights. There is case law indicating that whether a waiver is knowing and voluntary can be effected by severe mental conditions. However, there are many factors that would go into such an argument. Your sister should contact an attorney and make them aware of all the facts so they can know how to best defend her.
This answer is provided for informational purposes only. The response given is not intended to create, nor does it create, an attorney-client relationship. Each case is fact specific, and it is impossible to evaluate a legal question without a review of all the facts at issue. If you are looking for legal advice regarding a problem in the State of Georgia you may contact my office so that we can set up an office or phone consultation to fully address your question. http://www.kimmeylaw.com
Criminal Defense Attorney
To some extent it might also be helpful in evaluating her particiation in the crime and the punishment if she pleads guilty or is found guilty. Sonding like a broken record, but she really needs to consult an attorney to discuss these issues and how they impact her particular situation.