My 1 year old female pitbull?

Ok so we have had our red nose pit since she was 10 weeks old she is a rescue as are our other 3 pit mixes, I have become very familiar with the behavior and training of bully breeds and mixes. Our 1 year old has never shown any aggression towards people or other dogs she is very sweet and loves kids! But over the last few days we have had a totally unusual problem! She is attacking one of our other dogs! She has been kennaled with the other mix since she was 10 weeks and has always had a close relationship with the dog she is attacking! We have had to separate and use rather aggressive attitudes to prevent her from fighting! It literally happened over nigh with no signs! All are fixed and well trained I hate to use remote trainers but if she's gonna be aggressive I want her to know its not ok... any advise?!?!