She is super cute! The original puff ponies are perfectly fine to wash as normal. I have always had success just washing, air drying and brushing to get the poof back. But I agree with Jewel, you never know what may happen to a custom pony. The material used is likely not the exact same as the originals and may react completely differently. Not to mention you may accidently wash off whatever paint the customizer used while making her. Your best bet would probably be just to give her a good brushing and enjoy her as is, she is totally adorable as she is anyway!