Definition of a gamer
A person who plays video games or participates in role-playing games.
Technically, Facebook games are video games, so technically your aunt is a gamer.
I, for one, am accepting of the fact that gaming is becoming widespread to multiple platforms including Facebook. Twenty years ago being a gamer was seen as kinda weird and stuff. Now it's a social norm etc.
Don't hate on it, be glad more people are taking part in something that interests you no matter the format within which they choose to do so.