Some children just don't like them. Here are some ideas:
Do you have something interesting for her to look at during the ride or walk? Remember that at such an early age, her vision is not good for long distance. She sees about one to two feet clearly, just enough to see your face during feeding and play time. maybe try putting a toy hanging from the stroller's sun cover for her to look at.
Could it be the angle in the stroller she doesn't like? Maybe try putting her lying on her back or more of an angle. I didn't start using the stroller until my son was 3 months, he was born in a cold winter, and I would always have him lying down.
Maybe she's finding it too bright, add a blanket over the cover and the whole front to dim the sun light. For the car add a sun screen to the rear window.
Does she have a paci? I found the first car rides hard as well, a paci helped give him a comfort I could not offer while driving.
Could it be that the rides or walk are too close to a meal? If she's getting hungry she may not want to be in the motion provided by the stroller or car.
YOu could also try to go on those excursions when she is close to her nap but don't make a habit of it or it may become a prop for sleep. Make sure to put her in her bed when you get back home that is if she falls asleep.
You may want to hold off the stroller and try a child carier, you know the one you can strap on yourself and place your child in front or back. I loved those for public transportation or quick errands close to home in small stores.
Then again, she may be a grouchy or touchy child for whom those two activities may be to stimulating for her at this time.
Hope something in here helps out.
marty