Air carrier Flight Attendant reported being notified of a checked bag with a battery powered personal electronic device (PED) prior to gate departure. The Captain stated the PED had to be unloaded.

Narrative

After boarding was complete passenger came forward and advised me she gate checked her bag and forgot she had a laptop in the bag. I advised the gate agent and the gate agent told the passenger the bags are gone sorry. She asked well is it safe? The agent said no but if we pull the bag you have to come off the aircraft. The manager then came down and told the agent to hurry because we have another plane that needs this gate. The agent advised the manager and the manager asked the passenger if it was lithium. She states it's a small apple laptop and he said ok we are good close the door. I then advised the pilot of the situation; so he spoke to the manager and the manger stated it's not lithium so it can go. I then stated the passenger doesn't know if it's lithium all she knows is it's an apple laptop. The Captain then confirmed it was a lithium battery and it needed to come off. The agent was going to put the entire flight at risk because he didn't want to pull the bag. The manager was trying to coerce the passenger into stating it wasn't lithium so we could close and get the next plane to the gate.