My two female cats wont get along?

i have had my female cat poppy since a kitten, she is 4 years old and 2 weeks ago i adopted another female from a rescue centre who is 3 years old. when i first bought my new cat smartie home i did not realise poppy was in the house and they got into a massive fight resulting in poppy weeing everywhere. i split then up for a while and used a rag with each ones scent so they could get used to it. then they accidently met up again and got into another fight. i have no put them in a room together, supervised and whilst they havent psyically attacked each other poppy has been very hostile hissing and growling, smartie doesnt do anything back. will poppy ever at least tolerate smartie, i understand they will probably never be friends but i'd like to be able to leave a room or let them both outside at the same time with the knowledge they will just ignore each other rather than tear each other to shreds.