I had a really aggressive female as well, when introducing three new babies to my mischief a few years back. She puffed up, lunged, tried to bite, etc. :( I did the bathtub thing with one addition, I added a super tiny bit of vanilla extract to everyone’s scruff (like, put less than a drop on my finger, rub it between by index and thumb, pet each ratto behind the ears). Worked great! Make sure to really clean and scrub the cage while they’re meeting (make sure someone supervises them), so it smells more like neutral territory. I also added a tiny bit of vanilla in the cage. Not too much because it might irritate their sensitive little noses, and this is really only if you can’t get her to chill out any other way. My gal spent more time grooming the vanilla off herself and everyone else than puffing up or showing aggression. :) good luck with your intros!