>>44669667I always assumed she and Ghastly are kind of like a hard gas. It could knock things over, bite you, that kind of thing, but if you tried to touch it it would puff away like cigar smoke, then reform.
There are parts of them inside this gas that are clearly, visibly solid, like Misdreavus' Pearls or Ghastly's teeth, but I think a lot of it is harder to tell, like a foamy type substance, maybe.
It's something that doesn't exist in our world, which is I think a big reason they're so cool to think about.
Obviously this doesn't apply to every ghost Pokemon, Shuppet is obviously a cloth puppet, Pallosand is a sand castle, but this is how I interpret the more hazy ones.