They should've had an episode where they go to the Mirror Universe and for the rest of the series Troi would be replaced by her mirrorverse counterpart which would basically be Marina Sirtis playing herself.
Yeah but no one knows what she's all about. One moment she's on familiar terms with Q, the next she's popping up in 19th century San Francisco . Like who the heck is this bartender?
She's a near immortal. She was alive in the 19th Century and eventually met Picard later. She's a bartender because she likes people, and people talk in bars.