I've been researching sailor moon costumes recently too, so here is my input. (:
I'm not too sure about the pleating honestly. Pleats just aren't really made to flare, they mainly lay flat. But I would always suggest experimenting. Start by following her tutorial for the pleats, but just pin it before cutting the 'v'. Then you can experiment with different ways of attaching the skirt and which would lay the way you want. Also, if you add another chunk of fabric (make the skirt longer) then do more/smaller pleats it may lay differently. This also depends on the fabric. They are using a cotton, something like a satin would lay differently.
Also I've seen some people
gather and pleat their skirts (which is more Manga style, but I personally like it more than the flat skirts). That may work as well. Either way just try experimenting until you find what you want, and try not to cut your fabric until you are happy with it.
Edit: Also! I've seen people cut a circle skirt then pleat that into the waist band, that ends up with alot more fluffy goodness than just pleating does.
Edit 2! Here is a different tutorial that does the same thing as Pipsi's but has a circle skirt instead. Check it out