The pair were working at the time in the hospital’s risk and patient safety department where Ms Griffiths said “quite a lot of us” became friends with Letby.
Ms Griffiths said she had been aware of the concerns about the deaths and unexpected collapses of babies and a link to Letby since September 2016.
Shahram Sharghy, representing some of the families of Letby’s victims, asked whether she was “making light” of “most serious” accusations – which Ms Griffiths denied.
Mr Sharghy said: “Can you even begin to imagine and put yourself in the position of the families of the babies who were harmed when they see those messages?”
Ms Griffiths said: “I know … I am so remorseful.”
Earlier, the witness told counsel to the inquiry, Rachel Langdale KC: “I truly and deeply regret having started that conservation… this is completely unprofessional, poor judgment on my behalf and completely insensitive.
“And for that, I can only apologise from the bottom of my heart.”
The inquiry was also shown a letter that Letby’s parents – John and Susan Letby – sent to trust executives following the outcome of a grievance complaint that Letby submitted over her removal from the neonatal unit.
