This is an optional mission for Michael. This mission happens after the mission 'Friend Request'.
Amanda calls Michael, she'll tell him she has been arrested and asks for his help. You can choose to help her or not.
If you help Amanda, drive to the way point on your map. You will find her locked in a police car, steal it and lose the cops.
Once you lose the cops drive Amanda home, listen to the conversation and the mission ends.
You can choose to not help Amanda, but that will cost Michael $5,000.