Unsure if this is bannable

So im playing Nasus this game and at the start our team invades successfully but morgana (hopefully) unintentionally steals the buff and tilts the kayn but he still plays consistently which is okay, 4 minutes in morgana, ezreal, and kayn are arguing about the stolen buff which causes morgana to mute all (not a bannable offense) and proceeds to start trolling in bot lane by actively not helping ezreal and last hitting minions (to tilt ezreal), at this point the game is already a lost cause but we still play, morgana then starts to roam despite our entire team trying to stop her, starts going top and mid to last hit as well, at this point our team decides that morgana is actively trolling and we've lost the game, im unsure what happens next but from the replays the team decides to give up, all of us agree. Is this a bannable offense or is this allowed ?