It sounds perhaps like MaryK suggested that because she has so much energy and intelligence, she has found a good way to 'let it out' and stimulate/entertain herself by barking. From what I understand barking for dogs can be rewarding
in itself as a stimulating rewarding activity, almost 'something to do' to hear the sound of their own voice...even better if it gets a response from a human ('Be quiet' 'Shhh, I said No barking' etc, you don't sound as if you are doing this). My Mum's miniature schnauzer would bark at anything has now quietened down so much with more on lead walks and being given kongs and chew toys which tire her mentally.
More on lead walks sounds like a perfect idea

- maybe ask for eye contact at different times or simple behaviours or speed up/slow down the pace so her brain as well as legs are worked on the walk. There are also loads of free games and simple ideas inside the house that I use with Russell online that are really fun-from hiding food in cardboard boxes to quite complex games for v intelligent dogs which jenny might be (type in 'games to exercise your dogs mind' or similar) - then the simulation and reward comes from the things that are keeping her mind occupied and tiring her out mentally rather than Jenny barking to occupy herself.
As for the car - if at the moment it is the thing that happens everytime just before she is getting out - maybe she is getting sooo exited as she knows she is going for a run that she can't contain herself and will bark with exitement. I guess it would be similar when dogs go beserk when they see a lead. The majority of advice I have read with this is to
MAKE IT BORING. ie. do it over and over again without going anywhere exiting..maybe going to the car getting in then getting out, then mix it up sometimes go for a 3min drive round the block and back, get in then get out - so that car doesn't always equal walk which equals exitement. Then re-introduce sometimes going out for a run with the car.
With the added mental stimulation inside the house and the extra walks she is getting with you and the car no longer being the only guaranteed promise of a walk....hopefully that could help?