Ivanka worked as a senior advisor to Trump during his presidency.
The threat was linked to the US killing of a top Iranian general.
Twitter has suspended 70,000 accounts that have shared QAnon content at scale.
Trump is expected to issue more than 100 pardons and commutations.
There are questions over whether the US Constitution would permit such action.
The US President was permanently suspended from Twitter on Saturday.
The company's boss has outlined steps that would "build a better" internet.
"Parler has not taken adequate measures to address the proliferation of these threats to people's safety."
The Washington Post has released details of the call.
