Shelford was either sitting in a car or standing close to it when she yelled at Tangaroa Samuels: "Get him my son, get him. Pack him, my son, pack him up."
Sentencing her, Judge Keith de Ridder said it was highly unlikely her son would have delivered the blow had Shelford not encouraged him.
"You did nothing to stop your sons from assaulting Mr Lemon. In fact, it was quite the opposite. You egged them on, encouraged and provided verbal support," the judge said.
He said witnesses during her trial gave evidence Shelford used a variety of words that incited her sons to attack Lemon.
The violent attack was sparked when Lemon's special needs brother was intoxicated and stood at the front of the property on William Jones Dr, yelling abuse at passing vehicles.
Frederick Samuels was driving past and stopped his vehicle, got out and became involved in an argument.
Frederick Samuels left but returned with his brother and mother a short time later in three vehicles.
Judge de Ridder said Lemon came out, apologised to the brothers, and urged them to leave.
He said Frederick Samuels handed a piece of timber to his brother who swore at and threatened Lemon.
As Lemon momentarily turned to speak to a family member, Tangaroa Samuels swung the timber baseball style across the back of Lemon's head.
He was rushed to Whangarei Hospital in a serious condition but was soon flown to Auckland where he had surgery to alleviate the bleeding and pressure on his brain.
Judge de Ridder said Lemon's life has changed forever.
He declined an application by Crown lawyer Trelise Needham for minimum period of imprisonment to be imposed given the nature of the offending.
Defence lawyer Arthur Fairley said Deidre was remorseful and had submitted a letter to court in which she said she felt sorry for Lemon.