O'Brien's proposal to take annual leave wasn't accepted, Parkill said.
"Through your lawyers you just said: 'no'.
"Out of 220 people in the newsroom, you couldn't negotiate with Tova who has spent 14 years with you.
"You didn't even have a discussion with her," Parkhill suggested.
But Bristow said: "I didn't have a discussion with her ... because we were quite a long way apart in terms of our interpretation of the restraint".
Parkhill argued that "taking Tova out of the market, making her sit at home doing nothing" would mean she "can't work anywhere other than a bar".
But Bristow said "Discovery is concerned she is taking with her intimate knowledge and information she has built up at Newshub, and will use that potentially to benefit MediaWorks.
"She ... holds a key role at Newshub and is going to a direct competitor of Newshub in another key role."
She also said she believes O'Brien will have "her views on the editorial agenda for that show", such as what interviews she wants to do and outlining what stories would be covered.
ERA member Marija Urlich said she couldn't see any "give or compromise" on Bristow's behalf.
Bristow reinforced previously made comments that a sudden departure of a political editor is "extremely disruptive" to a newsroom.
She said a sudden departure would leave Newshub without a political editor and "effectively leave us one person down in the gallery at the time".
In terms of former Newshub political reporter Jenna Lynch taking on the role as political editor, Bristow said the company needs "time to be able to build her up as the new face for political politics".
Lynch starts in the new role on Monday, Bristow said.
She also confirmed her belief that Newshub and MediaWorks are in "direct competition".
She said the media landscape has changed significantly since Newshub was bought by Discovery.
"A large portion of the broadcasting landscape were owned by one company, so we're dealing with a different environment."
Bristow said the whole point of the restraint of trade was for "breathing space".
But Parkhill asked if the "breathing space" would have any benefit to Discovery whatsoever, other than a competitive benefit.
"It's to protect our propriety assets that Tova has access to," Bristow replied.
The launch date for O'Brien's new radio show Today FM hasn't been confirmed but is rumoured to be this month. If so, it would coincide with the return of TV3's new AM Show, expected back on air in February.
O'Brien often appeared on The AM Show and was broadcast on both TV3 and Magic Talk radio - harking back to when MediaWorks owned both the radio and TV networks.
Restraint of trade clauses are designed to prevent employees from jumping ship to work for a competitor.
In this case, Discovery will have to convince the Employment Relations Authority that O'Brien's new radio show is similar to her former role as a TV political editor, Newsroom reports.
O'Brien announced her resignation at the beginning of November last year in time to finish at Discovery before Christmas, take a month's leave, and finish out her contract in time for Today FM's launch by the end of this month. But then Discovery told her it would be enforcing the three-month restraint clause in her contract.
The hearing comes after the failure of mediation between the parties.
