My opinion:

If she loaned them her van (Or they rented it, or whatever), she should have known they would make a likeness of it. If it were my van, I would be stoked! the only downside would be people thinking you 'copied the onward van' rather than being the inspiration... that might get a little old, but I am sure she could get plenty of documentation from Pixar Studios to back her up.

Like DYNO DAVE said, this is a great opportunity! She can embrace this and really open the doors for a whole new generation of vanners to come through. This can help shed the stigma of 'Rape van, scooby van, murder van, etc.' Kids can look back on her van the same way most of us do the General Lee, A team Van, KITT, Airwolf, Herbie, and other great movie cars.