There are 2 issues. One is that you don't know what's going on. The second is that it is history and something for you to learn from. The money has been dispersed. If you don't think it should be dispersed in the future then you need to change the rules. If you and your PC come to an understanding then all is well. You can't punish the employee because everyone but you thought it was above board. You could punish the PC, but again she thought it was above board so there is a miscommunication, so would that even be fair.
You should discus it first with the PC and then possibly with all the employees as to what the rules are about loans, advancements, bonuses and such. Once everyone is on the same page, you hopefully will no have any further questions.
Related question: My employees are pushing to consider group health insurance rather than bonuses. (Yes I know it's cheaper to give a bonus... but) . I haven't talked to my insurance folks yet, but any great ideas before I do?
