I suggest to implement a new mafia role, a mafia sided jailor
You can -abduct a townie during trial, and jail if nobody was lynched. You can proceed to roleblock just like a jailor or have a chat with your prisoner.
He will reveal his chat to mafia but the prisoner won't see it
Then the gf can choose to kill the prisoner or kill a different person. If a killing role chooses the prisoner while he's captured, he will show up as dead in a jail cell.
When the gf targets you in a cell, it'll show up as jailor will execute you, to prevent cheat
This role will also show up as someone sneaking out at night, presumably same as a normal jailor.