Can you give a comparison of what her days used to look like as to what they do now that you've started EASY? It seems that if you are having to wake her for her naps, that she might be able to stretch to 3.5 or 4 hrs between feeds. However, Tracy generally recommended no more than 2 hrs at a time for naps or it could start to rob the night sleep. How long did she nap previous to BW? Just b/c she is 4 months doesn't necessarily mean you have to go to a 4 hr feed routine. That is a general guideline, so what you could do is see how long she does nap and feed her when she wakes.
Sounds like you are doing a wonderful job! I think she'll adapt very quickly, as having a routine is so comforting for the parents and the child.