Investigators say no foul play was involved in her death, and they are not releasing any more information.
Twaddell had left her home in North Coventry Township Thursday afternoon and was scheduled to work Thursday evening at Pottstown Memorial Medical Center.
She hadn't been heard from since.
Her family had been holding out hope for her safe return, and her brother flew in from California to help with the search.
Actress Kirstie Alley, who is a family friend, had offered a $25,000 reward and has also enlisted the help of other celebrity friends including Demi Moore and Denise Richardson.
Alley had been using Twitter to keep people updated on the case.