Stealing....?:
Since this is a family member, you have to work things out.  Confront them privately and tell them to stop it.  Threaten to tell the whole family if they do not repay what they took-not just from you but your entire family.  

Do not fall for sob stories.  The time for sob stories was before she took the money.  

What did she need the money for?  Gambling, drugs, etc? Then demand that she gets counciling.  If it was for a valid reason, then you need to be firm but fair.  This is not how people behave; especially towards family.

Avoid getting the police involved if possible.  This will only lead to being on Dr. Phil.  Change the locks and explain she is no longer welcome in your house.