Frankly, I think they've been using her alright outside the realm of magic; for one, there's her own reaction to the ongoing vibe between Elena & Stefan which, not only grants him immunity, but prevents Bonnie from making a move on him as well. It didn't take psychic powers for Bonnie to figure out Elena actually loved Stefan before she would figure it out herself IMO.
...Bonnie is seemed more of a tool/plot device. Even in the finale she was in the Bamon scene because she had to spell the casket and luckily give her a bit of lines...
Then there's also the somewhat instinctive distinction Bonnie seems to make between Caroline and the Salvatore, for her childhood friend was murdered - and therefore turned against her will - while the brothers chose this because of all the wrong reasons, like being with Katherine first and then with Elena when the orignal Petrova dumped them.
Even the so called "Bamon" scenes seem to me like they have more to do with this coping mechanism on Damon's part - in order to push any girl with a real shot at making him as emotionally vulnerable as he was with Katherine - than they have to do with magic, for the only kind of character development I've seen in both characters happens whenever each one forces the other out of his/her comfort zone.
Edited by wildling, May 13, 2012 @ 2:22 AM.