Susanna - who is normally on the sofa with Piers Morgan on GMB - is part of the new documentary, in which the 46-year-old journalist looks into the horrific events surrounding the death of 16-year-old Becky Watts in 2015.
Talking exclusively to The Sun's TV Magazine, the mum-of-three admitted that as a journalist you 'develop certain armour to switch your emotions off, but there are times when that armour crumbles'.
The TV favourite admitted that after talking to the parents of Becky Watts it really hit home and made her think about her own children.
'It does make you go home and hug your own kids that bit tighter at night because you see the true devastation of what some parents experience', she said.
Susanna is mum to three boys - 15-year-old Sam, 13-year-old Finn, 12-year-old Jack - all with ex husband Dominic Cotton.
And Susanna wasn't the only one to be affected by the harrowing documentary, as viewers took to social media to admit it left them in tears too.
The documentary examined how Becky Watts' killers Nathan Matthews and Shauna Hoare lied during police interviews.
Nathan Matthews, Becky's stepbrother suffocated the teenager before his girlfriend Shauna Hoare helped him dismember her body in March 2015.
Viewers took to Twitter to voice their heartache after watching Susanna Reid on the documentary.
One wrote: 'Honestly this Becky Watts documentary is harrowing. I'm actually in tears and feel sick', while another admitted that it had them in tears: ‘Crying at this Becky Watts documentary too close to home man R.I.P".
Another follower confessed it was 'tough' to watch while others simply described the show as 'heartbreaking'.
'That was a tough watch. Not just because its so close to home but just the pure evil involved. No parent should have to go through that hell'
A fourth follower simply said: 'Just watched the murder of Becky Watts documentary and I'm broken- that poor girl.'
Did you watch the documentary? What did you think? Let us know in the comments box below.