Sounds all too familiar. I feel your pain. I too have the 2 noise machines blaring. I didn't do EASY with #1 but planned to stick to it with#2-no nursing to sleep, no noise machines, etc. But when #2 came along, I wouldn't do it for fear if she cried a bit she would wake #1. Eight months into it, I have realized that it takes a lot to wake #1. Recently #2 has been screaming bloody murder at 5 am when she wakes because I won't nurse her. Instead I rock her but she still gets mad. And through all of it, #1 sleeps. And they are right next door to each other. So I would say, don't change what you want to do for #2 just because you're afraid #1 will wake.
Just wondering, have you started solids yet? Perhaps if not she is ready for the extra calories in the day to get her through. Another thing I am trying now is to reduce the time I nurse her (when I DO give in and nurse her). B/C even though she may not need the calories, the habit of being fed at 5a has trained her to get hungry at that time. Just as you or I will get hungry at lunch time, ect. So slowly decreasing the amount your lo takes in may help. I just started this this week so we can go through it together! Another idea I've heard is to try a water bottle. Something to soothe the tummy without the calories so her body stops expecting calories at night. All this was from a book I read this week. Hoping it works as I am soooo tired. #1 started sleeping better at 8 mos so I am hoping #2 will too. Let me know how things go and perhaps we can help each other. GOOD LUCK!