What a beautiful quilt!!
It looks like the petals are done using a stitch-and-flip method. I'm no good at explanations but I think a white rectangle is used and a colored square is sewn (on the diagonal) to the ends of the rectangle. then trimmed and the triangle is formed by flipping the colored piece---something like doing the corners of a snowball. At least, that's what it looks like to me. Someone else will probably give you a better explanation and info.
ranger