lol thanks for the confidence in me rinkins :)
well mats, as a mum of 2 i know pretty well how different babies can be. My daughter is now almost 12 and rarely sleeps through and yet my son did from 2 months.
I would suggest that perhaps you try and give her a bottle when she wakes at 3 to see if its hunger, at 4 months old she may well be going through a growth spurt.
She may also be teething, is she showing any other signs? that wakes babies up a lot as the teeth "jump" in the gum causing sudden pain.
As shes sleeping on and off it does suggest that is tired and that its something causing her to wake. Id try the bottle first to rule out hunger.