If she did in fact steal money, she could face criminal prosecution. She could also be sued for the amount she took, and possible for the costs of collecting it, too (e.g. court filiing fees; possibly legal expenses). If she did steal the money, she would be best served by returning it; she could certainly return it together with a letter in which she states that it was not stolen, if she wants to make it clear that she is not admitting to theft.