My DS2 just turned 4 months too so I hear what you're saying about transitioning to the 4-hr EASY. Some days we're at 4 hrs, sometimes 3.5, it kind of depends on how long he naps for. Right now for us, we're having a morning nap, an afternoon nap starting at 12:30/1:00, and a catnap around 5:00-5:30 for 30-45 minutes. We could definitely not go without the catnap. At this age I thought the catnap was still pretty typical. Could it be that the evening grumpiness is just overstimulation from the whole day and tiredness? When my LO is really tired, he will just wail when we put him down for a nap, but then with his soother he falls asleep within a few minutes, so I know he's tired. Maybe even if you can't get her to nap, you could try a really quiet activity in a dim room. Even if your LO only sleeps a bit, it might make bedtime easier so she's not completely OT.