Why does my cat pee on everything when she is with other cats?

i had 2 cats but my one cat would always pee on things and they would always get in fights. My cat always would pee on things though. there was a tabby female and a calico female. the one was older and one was younger.we had to give the calico to my aunt because she always wanted to be outside and our neighbors used pesticides. she is better with our aunt who lives in the country is there a reason the younger one would pee on everything?? how would i get her to stop? (p.s. both were rescues and spayed and we had 3 litter boxes. we took her to the vet and she doesnt have a bladder infection or anything.)