Especially so, given that this was not just a random van somewhere in the country, but one that was present specifically at a Pixar event. I don't know enough about intellectual property law to know whether seeing her van there and deciding to make the van in the movie look like it is a violation of any laws or a breach of any contracts, etc. Had they asked her to provide a van design for them, then do nothing about it or "buy" it, only for it to show up later in the movie, that would be a problem, I would think. Someone seeing her van at an event and thinking, that is cool, that would be great for those kids to drive around in something like that, I don't know what the law is. If that is a copyrighted piece of art, essentially, then yeah, it's probably an issue. By the same token, if animators used the Guggenheim as the basis to design a villain's headquarters, let's say, would that really be an issue? It may be a weird story in that the van itself is weird to begin with (the fact that it existed prior to the movie), but I certainly will not pass judgment on whether she has a valid claim.