The others have given good de-heading advice, so I'll jump to the mold question. It's hard for me to tell you just by the description if I think it's mold or not, but you could always try submerging her in an airtight container full of a hot (and I mean steaming hot) OxyClean bath overnight. OxyClean's pretty good at killing kill-able pony funk. Rinse her off and scrub her gently with a magic eraser (or even just your finger nails) when she comes out - if it comes off, great. If not, well, at least you tried! Also, have you tried some acetone to see if it's just staining of some sort? Most molds that cause problems will find tiny holes in the plastic and live there, but if there's a uniform fading of the spots after you scrub with acetone, that probably means it's just a stain of some sort.