Hi and welcome to the boards.
Hugs, I am sorry to hear that you are having such a rough time.
I am wondering if your lo could be over tired, hence the reason for her waking up so soon after a nap.
When you started EASY - did you go straight onto the 4 hour EASY?
Before you started the routine, were you feeding her on demand? If so roughly how often was this?
When you put her down for her naps, are you following her cues, or the time? You may need to watch her and see when her first sight of sleepyness / fussiness is, then check the time to see how long it has been since she woke up. This will give you a better idea of whether she can cope with the 4 hour EASY A time.
I am thinking that perhaps your lo may be better on starting on the 3.5 Hour EASY, and then once she is settled, you can try transition her onto the 4 hour.
It is also quite possible that your lo is going through her 4 month growth spurt.
Hope this helps.
Paula x