1) Use Cerberus and then cast Float and Shell on everyone, than throw all the GF power on Adel and Rinoa and every once in a while use a Triple Curaga on Rinoa (normally after 2 GF attacks). BTW, u better have Cerberus with a decently big HP because Adel casts Meteor and Smashing Blow the first time at small intervals. Until you use a G-Returner it might be too late.
That may work if your GFs are low leveled but higher powered ones could wipe her out in a single shot possibly. It all depends on your GF's and their levels. I know in my last game I never dared to use my GF's, as they would have killed her instantly.

2) Everything from above, except use all the Aura on Squall (if you have a big strength) because I've noticed that Renzokuken + Rough Divide does more dmg than a GF with all the boosting. After you finish Aura use the GFs. The only difference is that Aura is 20% of the time ineffective.
The only thing tricky here is Squall's weapon and certainity. Squall's weapon determines what kind of random attack he does next if he manages. Some hit all opponents on screen, so you could hit Rinoa depending upon what attack is used. It may or may not kill her, it depends entirely on which attack goes.

3) Everything in 1) or 2), except cast shell on Rinoa and Adel shouldn't be able to draw much from her nor you do big dmg with the GFs on her anymore.
I'm not aware if Shell lessens damage done by GF's. I never believed it did anyway. I just would stick to powerful magic, physical attacks, and controlled limits if you ask me but there are alternatives.