There are two modes of thinking about bastille's leadership zeta.
It's definitely good, but as soon as you have Jedi Knight Revan, you won't use her leadership zeta again for a long time, possibly forever. So the question is, do you want to zeta something that you know is going to be obsolete very quickly?
Now, I zeta's her before Revan was released, so i didn't know it was essentially a temporary investment. And gosh darn did it pump up my Jedi. It makes killing Palp squads downright easy. Nowadays, though, I think you can get Revan very, very quickly after you get Bastila to 7* (you should be working on the other requirements simultaneously).
The Jedi Revan event can be done without Bastila's zeta, assuming Bast is about g10, Jolee is g9, and the other 3 toons are g7-g8. Not only is this achievable, but you're going to want Jolee and Bast at high gear levels anyway.
So, it's up to you. If you think you'll earn enough rewards to basically trade 20 zeta mats and 13 omegas for whatever extra GAC or Arena booty you think you'll get, go ahead and zeta her. Otherwise ... especially if your other Old Republic toons are close to 7* by the time you get Bastila there ... you hold off and use it to instantly zeta your new Revan and he'll be a better leader for you anyway.
In any case, Bastila's lead is much better than GMY's, so bringing it just short of zeta is absolutely mandatory, even if the zeta ends up (depending on your play style and how far along you are with other Old Republic toons) being optional.
...Speaking of zetas... have you decided which toon gets your first?