I don't think that WD-40 is a good idea, because it could further stain your top.
Try blotting the spot with a solution of one tablespoon Dawn brand dishsoap to 1/2 cup of HOT water. Place the spotted area of the blouse on top of a WHITE facecloth or towel and apply the solution while still hot.
If this doesn't work the first time, try it again, but this time also cover it with a white towel or facecloth & run an iron over it a few times (if it is an ironable material).
Either way, the grease should melt into the white towel or facecloth and be almost invisible. Whatever remains on blouse or cloth can be easily removed in the washer on warm.
