This is so dumb it's a non-issue.
No one is being denied entry. It is the manner in which the tickets are being purchased (as a couple).
I can't put a "good friend" of either sex under my health care policy. Doesn't matter how many years I've known 'em and doesn't matter how much (s)he may need health insurance.
Nothing. My daughter, and her friends did exactly that for the jr/sr prom. They took a sophomore who was sad she wouldn't be able to attend prom at the old alma mater the next year because she was moving to Bastrop.
A few weeks later that friend died in a car accident. The girls were so happy that they had been able to share a special night of dress ups, and fun with each other, and that their friend had gotten to experience the prom with them
It wasn't about same sex coupling, it was about being with your friends on a special occasion.
Even back in the '60s the tradition was to have a "singles" table where students without traditional dates sat. Nobody asked them there if they were gay or not. Those tables were often the most fun, with prom goers coming on to each other, being pretty uninhibited, pairing off, and not on fake dates that so often happen with proms.
I'm as offended by people assuming that two people of the same sex going somewhere together are gay as I am about gays flaunting it.