It means she has a history of re-tweeting Tammy Bruce when she likes what she says.
Really, what has you so vested in seeing Mrs. Palin decide to abandon a run in 2012? Were you ruthlessly shot down in an amorous attempt upon her person at one point in time? Did Todd smack you around for making a pass at his girl? Or, going with the theme of this tweet, perhaps you're simply jealous of Mrs. Palin and have your eye on Todd?
Seriously though, do you understand the word “Obsession”?