"And if the woman's description of the film is accurate, her point is not so far fetched."
It's not accurate at all.
Elsa's non-magical sister Anna's shotgun wedding to someone she barely knows is meant to illustrate how "heterosexuals diminish marriage."
It wasn't a shotgun wedding nor was it showing how "heterosexuals diminish marriage." The girl was left alone all her life because he parents shut down the palace to keep people from finding out about her sister who was further isolated because they thought her difference was dangerous (Elsa almost accidentally kills Anna at the start of the movie) The first time a guy comes along and plays up to her (a low line royal in his own kingdom with no chance for the throne), the guy is trying to trick her into marriage, she falls for it. It's perfectly understandable.
What is the target age group? My daughter is in first grade and the girls are flipping TF out over it. She just went to a Frozen themed birthday party complete with broadway caliber singer and Piano accompanist.
IMHO (the H here stands for heathen), the overriding theme of the movie is how women don't have to wait for a man to sweep in to save them. They can be heroes of themselves and one another. That is an excellent moral statement. If the only way one can interpret that is to make it about homosexuality I'd pity that person.