My niece is was fired because she said she wanted to purchase a prepaid bank card and then was told that the card was missing.

My niece wanted to purchase a prepaid bank card from the HESS store that she worked at.She changed her mind and put the card back.Her manager called her (2/22/13) and told her that the card was missing.The manager told her that they had her on camera putting the card back but could not find the card.The manager asked her if she was sure she did not activate the card and she said that she had not. We left to go to the Bahamas the next day (2/23/13).We were gone until the 2/28/13.She was supposed to go to work 3/2/13 but received a text message stating that they were trying to cut back on hour and told her not to come in until 3/4/13.When she went to work on 3/4/13 she was fired.My niece count money and made deposits at the bank for this company numerous times.They saw her put the card back so they should be able to see if someone else took the card after she put it back.Is there anything she can do?They threaten to call the police if she did leave the store. They showed her no proof.