Carey-Jones said her sister recently told her that the doctors told her she didn't need the medication anymore.
"They tapered her off the medications, and she said she felt fine," Carey-Jones said.
The sisters declined to discuss what medication Miriam Carey had taken.
Despite reported claims by Miriam Carey's boyfriend that she had been delusional, the Carey sisters say they saw no signs of any problems. Authorities have not officially linked the incident to mental illness or any other factor.
"She has never disclosed anything of that nature, and since my sister is not here to speak for herself that statement in and of itself is very questionable," Valarie Carey said.
To the Careys, their sister was a "vibrant" woman who had everything to live for -- especially her 1-year-old daughter.
Miriam Carey, they said, wanted to teach.
"She always talked about teaching. Her field was dental hygienist, and she wanted to go further and give back in the field," Carey-Jones said.
The sisters are struggling to reconcile the woman they know -- loving sister, mother and friend -- with the one who authorities say was behind the deadly chase.
"When you see the information reported, it doesn't add up," Carey-Jones said.
The family is questioning whether shooting Miriam Carey was the only way to end the chase.
"We want to know if protocols were followed," family attorney Eric Sanders said on AC360.
"We are interested in finding out what happened. ...We are going to conduct our investigation, and we are not going to go with just what the government said."
Authorities have acknowledged no shots were fired from Carey's black Infiniti as it raced through the streets.
"My sister just totally didn't deserve this," said Valarie Carey, who was a New York police officer. "There are going to be a lot of different stories being told by people that claim they may know her. They don't. She was a law-abiding citizen. She had no political agenda."