Have Molly put a demon in it, then have the gas pedal do nothing.
Depends on how much Essence we have.
And heading into a fight, you can never have too much Essence.
But people inside other cars cannot see your car. Which means that they cannot avoid it, causing a monumental hazard.
Even in your limited example, it would require that there be virtually no other traffic, so that no random civilian sees the veil come up, nobody crashes into us thinking there is nothing there while we find a parking spot, and after we park, nobody drives by wanting to park while we remain there. It sounds like a tall order inside a city.
So git gud.
The point is to break contact for the thirty to ninety seconds necessary to lose the shadow.
Vehicular traffic is significant in a city, but this is hardly an insurmountable issue for a good or experienced driver. Especially on a weekend with no rushhour traffic.
Random civilian seeing us veiling is not an issue for a generic sedan.
Just cut into a supermarket car lot with multiple entries and exits, veil the car and drive out of one of the exits.
A body left in the nevernever long enough just becomes ectoplasm. Well mortal bodies do.
Long enough is too long to leave the thousand year old body of a Norse valkyrie demigoddess lying around.
Especially since, if she's working a necromantic ritual on one side of the veil, you have some idea of the kind of spirits that it might attract on the other side of the veil.
Even if someone cant simply attempt to reanimate her, the corpse of a dead Norse valkyrie probably makes for a pretty solid basis for making a terrifying undead servitor. Or something for an Outsider to drive around.
Lets not plan to just leave it lying around.
I am 99% sure that Dresden, if motivated, can cremate a corpse fairly trivially. Magic corpse disposal doesn't run afoul the laws of magic. Dead is already dead.
Cremating a body to ash IRL takes 1-5 hours at temperatures of between 700 and 1000 degrees Celsius.
The one time I recall seeing Dresden vaporize body parts was in Small Favor when he blew a foot wide hole through Tessa's torso, and that was after he'd gotten Soulfire.
On the other hand, if the Elder Ankou is rescued alive, Im reasonably sure disposing of bodies is in his portfolio.