I think this is common with the G2 glittery ponies. I know it certainly happens to the G3 glittery ponies.
Sounds like plasticizer stuff to me. There is a product called
Formula 9-1-1 that is supposed to help; I've not used this product personally. It can be harsh and may remove painted features, and you'd have to re-apply as the pony becomes sticky again.
You can of course try to just clean her up with soap and water and see what happens. You may have to clean a few times until the plasticizer stops leaking.
I know the G3 glitter gets ate by the plastic and such, hopefully someone who has experience with the glittery G2 can say if their glitter gets ate too.