When asked who the abductors could be, Khalid said only "gunmen", adding that a search for her was under way.
"This is a first for our organisation and we're really praying for a quick resolution"
Jeff Palmer, international director, Asian Rural Life Development
The organisation that she works for has not yet been contacted by her captors.
Mizell has lived for several years in Kandahar, where large numbers of Taliban fighters and criminals are believed to operate.
Mohammad Gul, a professor at Kandahar University, said she taught English at the university.
Gul said Mizell can speak the local language, Pashtu, and that if Afghans asked about her background she would say she was from the well known Alakozai tribe.
"She is a very patient and calm woman," Gul said. "She was always thinking about Afghanistan's future."
Jeff Palmer, international director of ARLDF, said Mizell had worked on income-generating women's projects in Kandahar for the last three years.
"It is our hope that our worker will be released safely and quickly and we are doing all that we can to resolve the situation," Palmer said.
"This is a first for our organisation and we're really praying for a quick resolution."
In the past criminal gangs and Taliban fighters have kidnapped a number of foreigners and Afghans.
Several Westerners, including two German construction workers and two Italian journalists, have been kidnapped in Afghanistan in the last year.
The latest abduction is the first kidnapping of an American in recent memory.