Speaking exclusively to ITV News, Dawn Bestwick said jail wasn't good enough for MIck Philpott and that "as a coward" he "deserved to die".
The judge has delayed her sentencing to "reflect further" on the trial Mick and Mairead Philpott and friend Paul Mosley.
Tributes have been paid to five brothers and their sister who died in a fire at their family home in Derby in May last year.
Mick Philpott will not face charges over claims that he raped two women, Derbyshire Police said today, due to "insufficient evidence".
In a statement, the force said: "Derbyshire Constabulary is not currently investigating any allegations against Michael Philpott.
"The allegations were reviewed and there was insufficient evidence for further action."
The rape allegations came to light during the investigation into the fatal house fire at Philpott's Derby home in Derby.
Philpott was found to have started the blaze, which killed six of his children. He is serving a minimum 15-year sentence for manslaughter at Wakefield Prison.
– Assistant Chief Constable Steve Cotterill
"We can confirm that officers from Derbyshire Constabulary are making inquiries into allegations of further offences committed by Mick Philpott.
"These allegations came to light during the investigation into the fire in May last year in which his children died. He, his wife and their friend were later convicted of the manslaughter of six children.
"Investigations are continuing and it would be inappropriate to make any further comment at this time."
ITV News Central understands that Mick Philpott, who was jailed for the manslaughter of his six children after a house fire in Derby, is being investigated over accusations of rape from two women.
Derbyshire Police say the allegations came to light during the investigation into the blaze.
Lanterns were lit in Derby on Sunday in remembrance of the six Philpott children who were killed in a house fire started by their father.
Jade, 10, and her brothers John, nine, Jack, eight, Jesse, six, Jayden, five, and Duwayne, 13, died last May.
On Sunday, Derby City Council confirmed its intention to knock down the property and the adjoining semi.
His wife Mairead, and their friend Paul Mosley, have been sentenced to 17 years.
A minute's silence has been held in memory of the six Philpott children who were killed in a house fire started by their father.
Supporters, staff and players fell silent at 3pm to remember Jade, 10, and her brothers John, nine, Jack, eight, Jesse, six, Jayden, five, and Duwayne, 13.
A minute's silence will be held today in memory of the six Philpott children who were killed in a house fire started by their father.
Derby County Football Club has asked supporters to join staff and players in remembering Jade, 10, and her brothers John, nine, Jack, eight, Jesse, six, Jayden, five, and Duwayne, 13.
A spokesperson for the club said the Rams will hold the minute's silence ahead of their fixture with Ipswich Town at Pride Park Stadium this afternoon.
Mick Philpott, 56, was jailed for life on Wednesday after being convicted of killing the children along with his wife Mairead, 32, and friend Paul Mosley.
Senior Liberal Democrats have not entered the row which has seen David Cameron back Chancellor George Osborne's comments that the case prompted "wider questions about our welfare system."
Mr Alexander said: "The Philpott case is an individual tragedy. Children have died in that case.
"I think that is where we should let that case lie. I would not want to connect that to the much wider need to reform our welfare system."
The Prime Minister agreed with the Chancellor that the Philpott case prompted "wider questions about our welfare system".
The Prime Minister said the Chancellor's remarks about the Philpott case "were absolutely right".
He said: "I think what George Osborne said was absolutely right.
"He said that Mr Philpott was the one to blame for his crimes and he should be held responsible but what the Chancellor went on to say is we should ask some wider questions about our welfare system - how much it costs and the signals that it sends.
"We do want to make clear that welfare is there to help people who work hard, it shouldn't be there as a lifestyle choice and I think that's entirely legitimate."
Shadow Chancellor Ed Balls launched a scathing attack tonight on what he called the "cynical, nasty and divisive" way George Osborne linked the Philpott case with the broader issue of state benefits.
Mr Balls said the "desperate" Chancellor had offended millions of hard-working people and was playing politics with a tragic case for his own political gain.