I'm so sorry that you lost her.
I was worried about her, so thank you for letting me know what happened.
Was it definitely a case of egg binding? Unrelieved egg binding is always fatal in the end, and she must have been severely weakened at the time you took her in. It's possible that the stress of the car ride might have made her death occur a little bit earlier than it would have otherwise, but please don't feel guilty about it. Getting vet help was the only chance you had at saving her, so you had to take her in as a responsible pet owner. She would have surely died if you stayed at home instead of taking her to the vet, and might have suffered longer in the process.
You did the best you could but sometimes our best just isn't enough. You can take comfort in the fact that you were actively trying to save her at the time she passed. Don't worry about anything that you could have done differently; no one has perfect knowledge, and you did what seemed best at the time. She knows that you loved her.