Mother-of-four Shelly May Freeman, 30, pleaded guilty to aggravated armed robbery, two counts of aggravated burglary and stealing.

Freeman and her two co-accused, Rose-Lee Clarke and another woman, picked-up disguises and weapons from Freeman's house on March 26 before driving from Launceston to Fingal to rob an elderly man.

Freeman's mother lived across the road from the man the three women planned to rob, with a victim impact statement from the man stating he remembered Freeman coming into his shop as a school girl.

The man said he'd let Freeman take lollies even on the days she had no money to pay for them.

On the night of the robbery, the women broke in to the man's first property but only got away with a six-pack of beer.

They managed to get into the house where the man lived and was sleeping.

The man heard people moving throughout his house then suddenly Clarke and the third woman appeared and began beating him with a hammer and a baseball bat.

During a 10 to 15 minute ordeal the women demanded money and repeatedly hit him, with Freeman shouting she had a gun and she'd shoot him if he didn't give them cash.

The man was hospitalised after the home invasion, sustaining a five-centimetre laceration to his skull that required stitches, broken teeth, a blood nose, and terrible bruising on his upper body and thighs.

During sentencing Justice Robert Pearce said the man arrived at the hospital anxious, upset and trembling as a result of the attack.

"This was a very serious home invasion," he said.

Justice Pearce took into account Freeman's early guilty plea, but noted she hadn't admitted her full role in the home invasion to police.

She was sentenced to three and a half years' jail backdated to June 6, but she would be eligible for parole after serving half. A six-week suspended sentence was also activated, but it would be served concurrently.