Car seat toys that attach to the car seat?
Baby music lullaby CD?
Bring a favorite toy, blanket w/you?
Make sure she's not hungry when you go.
A lot of my friends and cousins w/girls did this. It was a stage. My son never did. Sorry I know it's frustrating.
Does she ever fall asleep in her car seat like if you were to take her for a walk in her stroller? Then transition the car seat from the stroller immediately to the car? Just an idea if you need to do some QUICK grocery shopping.
If it's too much (and I completely understand if it is), maybe you could run your errands w/o her when you leave her at home w/your hubby or family member.
Could you take her for a walk in her car seat that goes in the stroller to kind of make a calm transition? You know just a short walk then end up at your car in the driveway & put her car seat in to go? Just an idea.
This stage will pass. Try to rack your brain to find ways to work WITH this issue instead of against it. I know it's hard but it will pass.