The girl told me what's wrong with "right to work" is that it means that the union will have to legally represent anyone in the shop even if those people don't pay dues. The big thing that unions spend their money on is representing people legally. Legal costs are very expensive. If the union has to represent people who don't pay dues, the unions will be bled dry paying for legal fees for people who may not have even ever paid into the union. She says it'll be a slow, several year death, but ultimately, will kill the unions.
Ive heard of this argument as well but I dont actually understand what kind of legal representation the union has to offer a non represented employee and what kind of representation it offers a represented one. Ive never actually heard of anyone ever getting a union lawyer for anything. The only time I have heard of union lawyers is when the union sues the company for breach of the union contract and almost always the union either looses or wins no significant victory.