A judge sentenced Gambino to 29 years in prison.
Eddie Hime, Sanchez's father, scoffered at the plea deal.
"Twenty-nine years for taking that away is not enough in my opinion," Hime said.
Jennifer Burke, Gilliland's sister, showed Gambino pictures of her brother.
"I can only hope that you suffer every day," Burke said. "You wake up and endure sleepless nights because your guilty conscience is eating at you for what you have done."
Gambino's attorney called the killings the result of stewing domestic violence, mental health issues and infidelity.
Gambino spoke to the victims' families and apologized for what she had done.
"I hate this happened. It's a horrible tragedy, not only to these people, but to my family," Gambino said. "I can say I'm sorry, but I don't think they'll accept it anyway."