At what point would there be road blocks?
Heard a guy from China interviewed yesterday. He had to alter his way to work because some dude was blocking a through street to prevent anyone but street residents from passing.
Most preppers have alternate plans to avoid interstates. This scenario you have brought up may be the exact opposite of what we think might happen. The interstates would be the last to close. We don't need to revisit the JIT inventory issue. Trucks will run. (if there are willing drivers and if they have products to haul) There isn't enough man-power for "SHOW ME YOUR PAPERS" road-blocks.
Do you know any trusted truckers that might pick her up?
Back up. Do you think the colleges are willing to provide the necessary resources to deal with quarantines? I don't. The schools will call for extended spring breaks and send them "anywhere but here".
What good will it do you to pick her up if she is shedding virus and you ride 6 hours in a car? Ask the cruise ship passengers or the airline passengers. We'll do ANYTHING for our kids. Do you have a trailer that you could put her car on and have her ride in it until you get home to your "sick room"? You do have a separate sick room right?
I don't expect responses for my rhetorical questions. Just throwing some of my thoughts out.
Very best wishes for you and your family.
Always remember the old saying: "Better to be a day early than one minute too late"