I just looked at that item. It doesn't look like there are any morphs in it to adjust the skirt away from the legs when the legs are bent.  Some skirts have a forward/ back morph that allows you to move the skirt out from the legs to prevent intersecting.

I would suggest having a look at this thread:

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2517340&page=1

It might be possible to use the skirt in the cloth room so that the skirt follows the figure's pose.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi