Ah, got it - hadn't worked out you were feeding again at naptime (I'm cutting back on coffee so I'm slow on the uptake LOL). So if you give her a paci instead of the breast, no go? Around 3-4 months I did have to do a sort of "snack feed" at naptime; I just offered one breast and that was enough to suit her. Maybe offer one breast and then paci if she still seems to want to suckle? Give your other breast time to refill properly.
Green poos can also be a sign of a food intolerance, so she could be reacting to something in your diet. I was cutting out dairy while nursing DD2 and drinking rice milk instead, and I didn't realize that the brand we were using had carageenan in it, and we got green poos from that so I had to switch out for a few months. (It was the lovely ladies here that pointed out the possibility!) Dairy and soy are common food intolerances; if her tummy is bothering her, the discomfort might explain the short-napping and inability to extend the nap.
Just throwing out some ideas here.