Is Hilary Duff using sound devices?

Is Hilary Duff following in the footsteps of Ashley Simpson and Britney Spears? While on Duff's 2008 Dignity tour in Monterrey, Mexico it was rumored that she was lip-synching. The footage that was released of the concert makes it look like Duff was not really performing her songs, but instead mouthing the words into the microphone.

A rep for Duff said that the equipment was locally used and the microphone was set on mute. Duff's lips were moving but there was no sound. The rep told E! News, "It was faulty equipment. There was no sound coming out, but she was singing. She was not lip-synching." Duff's publicist said that she does her own singing. "Duff has three more stops in Mexico this week, including a show Monday night in Puebla, before moving on to Brazil and Australia", said E! News.