A girl accused of killing her parents and younger brother says she was still traumatized by their vicious deaths when she accepted a jailhouse marriage proposal from the much-older man she blames for the murders.

The 13-year-old, on the witness stand at her trial Wednesday for the second straight day, was grilled repeatedly about her actions in the hours and days after her family members were slaughtered in their Medicine Hat home.

Crown prosecutor Stephanie Cleary asked during her cross-examination why the girl would agree to marry her boyfriend Jeremy Steinke, 23 at the time, if she was as horrified by her family's deaths as she testified she was.

"My psychologist says it's post-traumatic stress disorder," the girl practically whispered to the court.

Mr. Steinke, now 24, also faces three first-degree murder charges, but has not yet entered a plea. No trial date has been set.

The girl - the only witness called by the defence - first took the stand Tuesday. She told the jury her side of the story about how her parents and eight-year-old brother were repeatedly stabbed and slashed by Mr. Steinke in the family home in April 2006. She wept repeatedly when relating the details of her brother's final moments.

But on Wednesday she kept her composure and appeared to glare often at the Crown prosecutor. She was repeatedly told to speak up by both the judge and the Crown and often answered questions in just a few words.

The girl denied the Crown's theory that she had planned the attack and said she didn't call police or go for help because she was in a dream-like state.

"I was like a zombie - I could barely function," she said. "It didn't even enter my mind to call 911."

Clad in a high-cut brown top with her brown hair flowing over her right shoulder, the young teen remained stony-faced as she again recalled how her brother died.

She admitted she had wanted her brother to go to sleep and "to not remember this" when she started choking him with one arm, but he fought back and screamed at his sister to stop. She then pushed him into a bedroom.

She testified that when Mr. Steinke came upstairs after stabbing her parents repeatedly in the basement, he told her to kill her brother. But after stabbing him once in the upper body, she couldn't do it.

"I thought he was going to kill me ... because I couldn't do it," she said of Mr. Steinke.

She said he fled the house after her parents and brother appeared to be dead. Despite being alone in a home literally soaked with blood, she didn't bother to check if anyone was still alive or needed help.

"I wasn't thinking if they were dead for sure," she told court. "I was practically sleepwalking."

Ms. Cleary pointed out the girl had plenty of opportunities to ask for help. She stole her mother's purse, called for a cab, withdrew money from a nearby 7-11 bank machine with her mother's card and then headed to Mr. Steinke's trailer.

She didn't ask for help from the neighbours, the convenience store clerk or the cab driver, Ms. Cleary said.

On Tuesday, the accused testified that she and Mr. Steinke had "hypothetical" conversations about killing her parents and her brother. She said she would vent to Mr. Steinke because her parents didn't approve of their relationship.

But she reiterated Wednesday that she was just joking and didn't mean any of it.

The Crown's cross-examination took little more than 1 1/2 hours. The defence rested its case immediately afterwards.

The girl can't be identified under provisions of the Youth Criminal Justice Act because she was 12 at the time of the slayings.

Closing arguments are scheduled for Friday. Jurors will then be sent home for the weekend before hearing the judge's charge Monday. They will then be sequestered to deliberate over a verdict.