I think Tara gained more and more subtle confidence between Willow choosing her over Oz onwards - i mean with all the "just trying a little spicy talk" comments and everything
but for me the defining moment for tara apart from in 'Family' was when she actually left willow (sorry for bringing it up , not a pleasant topic) in Tabula Rasa . although Tara had been building on her own insecurities it was the action of leaving Willow when she needed to that defined a new era of Tara Maclay as her increased confidence and self-assuredness as a woman are more clear .
i mean the whole levitating thing in OMWF couldn't have hurt either

......not hurt at all i think .......quite to the contrary....
Sweetjane