First of all, you have done a remarkable job. This is some kind of a record that you have trapped the entire tree pile group. When working with ferals, you almost always have to resign yourself to the fact that someone will never be trapped. Years ago I hired a professional live animal trapper (humane, they were going to hand the cat over to me) to get a female who had repeated litters...just in case they could think of anything that I did not. Never got her and she died having the last litter, along with the kittens. But you have done it and I hope that you have taken some time to congratulate yourself and realize what an accomplishment this is.
IMO, yes, Stormy's presence could aggravate Milly. It is not on you though as Milly is a very intense cat and you have to proceed with the project that you started whether or not Milly is okay. The fact that there was some calming down previously is a good sign.
Lippy will stay at the rescue for 2 days if I am understanding you? Give it a chance that when Lippy returns that Milly will relax.
IMO, yes, Stormy's presence could aggravate Milly. It is not on you though as Milly is a very intense cat and you have to proceed with the project that you started whether or not Milly is okay. The fact that there was some calming down previously is a good sign.
Lippy will stay at the rescue for 2 days if I am understanding you? Give it a chance that when Lippy returns that Milly will relax.