Ms Smith told Breakfast: “Had he stabbed Elli outside of the apartment in the communal hallway, the starting point would be 25 years, and then the sentence would go up from there.
“If someone is stabbed within a home from a knife from their own knife block, the starting point is 15 years.”
She called for the gap to be “corrected”.
A Home Office representative said the government planned to “halve the level of violence against women and girls within the next decade”.
“This begins with improving policing and the criminal justice system, relentlessly pursuing dangerous offenders and providing sustained support for victims,” the spokesman added.
A minimum 25-year sentence was introduced in 2020, external for murderers who carried a weapon to the scene of the crime.
Ms Smith said it was “brought in with the best of intentions because of knife crime… however, what it created was a disparity”.
