That is a really good question because sometimes the person can be a bit too much and do other things like talk to or troll your friend (This has happened to me once apon a time) it's going to be really really hard to ignore them especially if they are the stalker type of bully (like mine was) but it is best to ignore them until they stop. If they join you in a room and start poking fun at you and your friends block them and make sure they block them also. Though at first it can be embarrassing as the days go on, they will target you less and less. Just please make sure to inform your friends as I have lost friends to a situation that happened to me personally in the hands of a stalker/bully. Don't give out personal information either as they can use said information against you. Stay Safe!