I can't really decide, especially since I haven't seen the trailer.
If they trailer made itself out to be a F&TF style movie, then yeah, that's annoying and I can understand why she'd want a refund,
However if she simply interpreted it that way, then the movie doesn't have to live up to individual expectations.
essentially was it false advertising?
which would be hard to claim, given that trailers are made from scenes in the movie,
everything in the trailer would have occurred in the movie,
Perhaps the theme presented by the trailer was false however,
You could take a movie like machete and make a trailer showing it as a romantic comedy, would that be false advertising?