Fondant and buttercream together - will this work??

Hello everyone!! Hope you are all well :-)

I am about to embark on my first barbie doll cake. I have decided to do it with ruffles in the front and a bit at the bottom, but with a smooth bit on the top. Princessy. Now I think it will be quicker and easier to do the ruffles with buttercream and the wilton petal tip, than making them out of fondant... But, the layer of dress that will go over the top has to be fondant. Will it destroy the buttercream ruffles or be okay? I was thinking of doing the ruffles and letting them set first in the fridge, so that they are hard, then draping the fondant layer over.

Will this work? Or should I do it all in fondant? Hopefully someone else has tried this before and can give me a heads up :-)