Do I just have to max out my Paragon (or Renegade) to talk to her and get her back on my side?
I believe it is too late to fix at this point.
You needed to have high enough Paragon during the Miranda/Jack confrontation in order to resolve the situation without losing either of their loyalties.
During the Final Mission, make sure you don't use her to lead anything. Pick Samara to hold up the shield and leave Jack behind to hold the door.
If you take Jack with you to fight the final boss or use her to support the shield, then she will die every time without loyalty.
Should I just bring her with me to fight the giant, not very cool human reaper?
I took an unloyal Tali my first time through and she died. Not sure if it is a guaranteed thing or not, but I think it is.
This post was edited on 2/18 at 4:31 pm