Murderer Angelika Gavare will not be prosecuted over an alleged prison assault on Ashlee Polkinghorne, the Adelaide mother in jail for the manslaughter of her daughter Chloe Valentine.

Gavare is serving a life sentence with a non-parole period of 32 years for killing Vonne McGlynn, a Reynella pensioner in her 80s, in 2008.

The alleged assault on Polkinghorne happened at the Adelaide Women's Prison in May last year.

A month earlier, Polkinghorne was sentenced to seven years in prison with a non-parole period of four years and nine months for manslaughter by criminal neglect.

Her daughter was repeatedly put on a 50-kilogram motorbike in the backyard of the family home at Ingle Farm in January 2012 and filmed crashing into objects.

The assault matter involving Gavare was listed for a pre-trial conference this month but the prosecution dropped the charge.