I've always found that brutal battles don't happen during free range (no fence at all). But, if you want to take her down a peg, you could prevent her from free ranging as well.
Many people wait to incorporate until they're the same size. I've never done this because I don't have the space. If you stop the look-dont-touch for a while, you will need to do it over again. No real issue on the laying/mating in my opinion. They're not very different in age.
Is it one girl...
The best scenario would be a "look dont touch" period of two weeks wherein the two groups are divided by chicken wire at all times. If you can't do this, then bringing them out daily for a few days or weeks will help. The movement for the new girls into the henhouse itself will be problematic...