A woman with bipolar disorder "forfeited" her right to be a mother when she served her children drugged hot chocolate before setting the house on fire, a judge said Thursday as he sentenced her to six to 20 years in prison.

Tanya Friedly, 33, of Warren, a Detroit suburb, pleaded no contest last month to one count of arson and two counts of assault with intent to murder.

Macomb County Circuit Judge David Viviano also ordered Friedly not to have contact with her son and daughter, who were 13 and 10 when she took them out of school early on Nov. 18, 2008, and told them she was going to a psychiatric hospital.

She then gave them hot chocolate, which made them "lightheaded and drowsy," and set their home on fire, her son wrote in a letter to Viviano that was read aloud in court. Neither child appeared in court, and Viviano asked news media not to identify them or the guardian now raising them.

"We're all going to go to a better place now," Friedly told her son that day, he wrote. He then ran out of the burning building along with his sister. Friedly was pulled out by a neighbor.

"My mom should be gone away for a long time for what she did," Friedly's son wrote to the judge, saying he was "emotionally scarred for life."

Friedly, appearing in court shackled and wearing jail clothes, apologized.

"I love my children unconditionally, and I was sick," she said, her voice breaking with emotion. "The worst punishment I can have is the loss of contact with my children."

Viviano noted that Friedly by all accounts was "a loving, devoted mother" but suffered from bipolar disorder with depression and anxiety.

"There's no question in my mind that you had and continue to have a serious mental illness," the judge said, though not reaching Michigan's legal definition of lacking criminal responsibility for her actions.

Macomb County assistant prosecutor Michael Servitto said the six-year minimum sentence will give Friedly's children time to grow up before having to confront their mother again.

There is a "special bond" between a mother and her children, Viviano told Friedly, adding that her actions "severed that bond forever" and "forfeited your right to raise your children and be their mother."