C.H.
As someone who travels to CA often, I would say to do your best to get a non-stop flight. It really adds to the length of the trip to have to stop. And often the hardest part for babies is the takeoff and landing because of the pressure change, so if you can reduce the number of times that happens, that could help.
Aside from that, bring food, favorite book, favorite toy so you can entertain her. Good luck and have fun.