A series of text messages from January 4 obtained by ProPublica detail Kimberly Guilfoyle's fundraising efforts for the event and how she also pushed to include more far-right speakers to appear alongside Mr Trump.
The texts are the strongest indication to date that members of the Trump family's inner circle were directly involved in the financing of the “Stop the Steal” rally, the nonprofit investigative newsroom reported.
Ms Guilfoyle has been dating Donald Trump Jr since 2018.
Text messages also revealed that Ms Guilfoyle was aggrieved that she had not been asked to speak at the rally.
Katrina Pierson, the White House liaison for the rally, told Ms Guilfoyle that it was Mr Trump who set the limited speaking line-up.
Ms Guilfoyle replied she had wanted to introduce her boyfriend on stage and that she had “raised so much money for this".
“Literally one of my donors, Julie, at $3 million,” she said, in reference to Publix supermarket heiress Julie Jenkins Fancelli.
It is unclear if that amount had actually been raised and, if so, how it was spent. Some of the money from Ms Fancelli went to “dark money groups” that supported the January 6 rally, ProPublica reported.
Ms Guilfoyle did, however, appear on stage the morning of the event to introduce Mr Trump Jr.
She also attempted to influence the speaker list by adding leader of the “Stop the Steal” movement Ali Alexander, former Trump adviser Roger Stone and conspiracy theorist Alex Jones, all considered too radical by Trump aides.
No novice to fundraising, Ms Guilfoyle was appointed in January 2020 as the national chair of the Trump Victory finance committee, which raised money for the former president's re-election campaign.
A US House committee has to date ordered more than 30 of people close to Mr Trump to give evidence about information leading to the January 6 insurrection at the Capitol.
Former White House chief strategist Steve Bannon surrendered to authorities this week after he was indicted for defying a congressional subpoena.
The committee last week subpoenaed another 10 former Trump allies.
Six of these, including former senior adviser Stephen Miller and former press secretary Kayleigh McEnany, were subpoenaed for reportedly scheming to overturn Mr Trump's electoral defeat at a luxury Washington hotel on the evening of the insurrection.
Ms Guilfoyle has not yet faced any scrutiny from Congress.