Have you tried booster seat? Something that's elevated and she can see out the window. Here's a picture of one I have:
http://www.yorkietalk.com/forums/my-...at-tested.html
If you do a search here for booster seat or car seat, you'll find members that have different type and their experience with them. One of the member (Matese) also had good results with these car seats for her furbutt Cody.