Hi, that sounds about right. For a 4 month old the approximate maximum awake time is2-2.5 hours, before they need to nap. I'm not sure if you swaddle, but it can help, also ensuring you have a good wind down ritual before nap and bedtimes...see p 181-182 the Baby Whisperer Solves all Your Problems. It sounds as though the day gets progressively difficult- which could indicate increased tiredness throughout the day, plus the falling to sleep, then waking, constantly - falling asleep, probably when she is exhausted.
I would make sure you really observe her, so that you don't miss the window of opportunity to get them to go down more easily, once past this you're into the overtired realm and it becomes much harder to get them to sleep.
Keep activity times short and not too stimulating, act on your observations, rather than sticking to EASY exactly.
Use the 4-S wind down ritual.
Use pat/shh to help her get off to sleep, but try to let her do the last little bit of falling asleep herself, in her crib.
Give these a go for a few days adn see if it helps.
Let me know how you do or if htere is anythign eles you want to discuss.