You could explain it like running mates are a married couple. If one of them dies (drops out), the other one legally has access. Everything goes to them.
Your boss would be correct if a completely different person tried to inherit those campaign funds.
They probably get their news from the typical right wing, Fox style, outlets. They say “is this legal?” And then everybody starts to think questions are reality. I feel bad for your boss. Being that brainwashed.
The icing on the cake would be her running against this country‘s biggest misogynist