Problems with Maddie's Cupcake Dress add-on

Wolpi

Is there anybody out there who calls her own the Cupcake outfit + the nice add-on "Whispering petals", that changes the base appearance completely?
I succeeded only one or two times by accident to change the top, the shorts and the socks into the far more beautiful add-on outfit.
I know, that I first have to put on the base clothes and then go to choose the "WhispPet-mats" (by the way: why are there two different folders "SF_PS WhispPet" and "SF_PS WhispPetP4"??). But when doing this, the base piece disappears and there's only the frilly seam left!

I tried and tried all combinations because I've saved one successfull attempt in the beginning and so there must be a way. But I can't find it.