
All I saw was a puff of smoke over her head, I think the buff was Fel Transformation? (I should have moused over it, and not get rid of my UI... v.v)
And she wasn't aggressive to me at all, just my pet, but that thing... o.O
EDIT: Found out what it was, from the spell Felblood link: http://www.wowhead.com/spell=80174#comments