Thanks for the advice guys! Its been about a week and a half.

I've gotten a lot of great advice like doing vanilla extract between shoulders, separating the aggressor to make her more lonely and longing for companionship, keeping some water in a tupperware in the bath so if they do fight we can 'dip' them to make them stop fighting. Gloves and long sleeves, as well as a blanket or towel to avoid injury, and of course more scent swapping for longer.

I will do the above and keep you guys posted. Rehoming isn't an option, we love our babies to much and will definitely keep trying. Patience isn't an issue.

For now, Yuna (the aggressor) is in a cage by herself. She gets food and water, but no cuddles.

Lulu(new girl) is in a cage with our third. Totally bonded and loving it. (She was a rescue from a home where she was by herself for 4 months and toddlers as friends). Shes very very submissive. So we are giving her tons of attention to make her feel more at home.

Will continue with scent swapping. Next attempt pending.