Cats fighting

I have 3 cats, a 6yo, a 5yo and a 10 month old

5 and 6 aren't friends but coexist just fine however the 5 yo HATES the kitten, avoids her and hisses and growls whenever she enters the room

Any advice on helping them get along, we followed all the introduction guides in the beginning

5 yo used to hide in my room but now it's the kittens favourite spot so I'm missing my baby's company and I hate seeing them both stressed unfortunately rehoming is not an option.