OK, we resolved the issue with my daughter. I confessed to her that the stuffed cat was not really married to the stuffed bear because lacked the power to marry them (I told my three year old this ONLY after I obtained her promise not to report me to the Bishop for violating Canon 1379). Therefore, the cat and the bear were not married.
I used the opportunity to remind her that the only way she could get married was by a priest in the Church, when the time came, and that a civil marriage before a judge or a protestant minister would be no more valid than my marriage of the stuffed animals. I also reminded her that she promised that I could pick out her husband when the time came.