I had to rip out all I've done, today I commenced with a slightly different technique. The basic circle of chain stitches, slip stitch; the main pattern consists of one double crochet and one chain stitch. This way little windows come into being, when making the double stitches don't prick under a heart but into the window instead.
It's faster, easier (hit the big window hole is easier than the heart) and airier. I hope she'll be contented this time.