I think the only thing that is going to help is repetition and patience. She's still in her adjustment period, and is having a hard time with the vehicle. Do you have a soft blanket in her Taxi that already has her scent on it? Do you bring a favorite toy so she has something to do? Do you keep her where she can easily see you? Do you play music quietly in the car? Do you talk to her soothingly while driving? Do you make sure she goes potty before taking her on rides? Do you give her a treat when you put her in her taxi and then when you take her out and praise praise praise?
Time. I think that's all it will take. Try to take her for a spin every day, even if it's just around the block. I am guessing there will come a time when the words "want to go for a ride?" will send her into a joyful frenzy!!
Good luck!