Was i wrong to fire the nanny?

i work until 9 at my job at Peet's Coffee Monday-Wednesday and Saturday and my godfather (the only adult in the house) works until midnight every other Wednesday so i used to have this old friend babysitting the two little kids in the house (my god dad's niece and nephew) on the nights that we cant be home. but one night i sat down with Jamie (11 years old) and he told me that my friend would hide in the closets and jump out to scare the kids. she thought she was being funny, playing a game, but Jamie's sister Ari would get nightmares from it. i asked her to stop and we got in a fight and i fired her. was that wrong? should i have given her another chance? now im out of a babysitter and getting my salary cut by the hour... should i just hire her back or what?