A single mother with terminal cancer is suing for the right to get medical aid in dying, and joining a campaign to make the practice legal in California.

Christy O'Donnell, a 46-year-old attorney and former police officer, is one of four terminally-ill patients who filed a lawsuit last week challenging the state law that makes it a crime to "aid, or advise, or encourage another to commit suicide." They argue that it should not apply to doctors who provide end-of-life drugs to mentally competent, terminally ill patients.

O'Donnell tells her story in a YouTube video posted by Compassion & Choices, an advocacy group that also worked with Brittany Maynard, the young woman with brain cancer who got a legal prescription of drugs to take her own life in Oregon last fall.

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O'Donnell was diagnosed with stage 4 lung cancer in June 2014, even though she'd never been a smoker. Despite aggressive chemotherapy, the cancer has grown and spread to her brain.

"The most likely way that I'm going to die with the lung cancer is that my left lung will fill with fluid, I'll start drowning in my own fluid," O'Donnell says in the video, which the group says was recorded on March 4th. "I spend an inordinate amount of time being afraid of the pain that I'm going to endure. All of that time that my mind spends thinking about that, I am not living."

O'Donnell says that while she worries about the pain, she is not afraid to die. "But not being afraid to die is not the same as wanting to die. I don't want to die."

What she does want, she says, is the legal right to obtain a lethal dose of prescription drugs to use when she's ready.

"I should be able to get a prescription, have that peace and never think about it till the day I'm ready to die," she says.

Throughout the video, O'Donnell's 20-year-old daughter Bailey sits by her side, fighting back tears.

Along with the lawsuit O'Donnell and the others filed in California Superior Court, the issue is dividing the state legislature, where a bill called the End of Life Option Act was recently approved in committee.

CBS Los Angeles reports the proposed law would require two doctors to agree that a patient has less than six months to live, and the patient must discuss alternative treatment options with a doctor. Then the patient must submit one written request and two oral requests before a doctor can issue a lethal prescription.

Doctors would not be required to participate or to refer patients to other doctors for a lethal prescription if they don't want to.

But critics raise concerns that some patients would still be vulnerable under the act.

"We know that as soon as this option is introduced, it immediately becomes the most efficient, expedient, and least expensive end-­of-­life option," UC Irvine Medical Ethics Program Director Aaron Kheriaty told CBS Los Angeles. "And we know that the medical system currently is under tremendous pressure to lower costs. This is, I think, a deadly mix. This is a mix that is going to put especially individuals that don't have access to the best medical care or insurance, this is going to put them in very vulnerable positions."

Supporters of the bill deny anyone would be pressured to end their life.

"Nobody gets forced into this option if they don't want to," said State Sen. Bill Monning, co-author of the End of Life Option Act. "We know there are some who have religious principles where they don't support this end-­of-­life option. We don't seek to change church doctrine. We don't seek to enforce this on anybody, only a voluntary patient, working with doctors, are engaged, voluntarily."

The California Catholic Conference says it remains its steadfast position when it comes to what it calls "assisted suicide" and any attempts to legalize it.

Five states currently have laws allowing medical aid in dying: Oregon, Washington, Montana, Vermont and New Mexico.