Is she breast or bottle fed? It could be a growth spurt - when does she start waking? If that's the case try upping her oz during the day if you bottle feed, and breast feed her when she first wakes to see if that helps if you breast feed. This is an age where the 4 month sleep regression occurs so hugs for the rough nights!
Also, can you post your easy so we could see if it may be an OT issue (doesn't sound like it from what you've written).