If you clean out her ears and look closely at the wax you've expelled, if it is mites, they are large enough for you to be able to see moving around. Many times they are covered in the wax however. I did a search for earwax in pigs but didn't come across any pictures. Just sites explaining the problem. I will list the links to the pages I've found.
Guinea Lynx :: Ear Mites WikiAnswers - How can you tell if a guinea pig has ear mites
If your pig isn't shaking or continuously scratching at it's ears, it's probably just wax, but should still be cleaned to prevent fungal bacteria from growing.