No, it's not "ok" to call people gay.
You call people gay if they are attracted to members of the same gender. But it's really better to call people by their names.
because much gay
Gay women can also be called lesbians, but the best thing to call them is "women".
they usually call them by their names, but I think the term you're looking for is "gay".
People would call them gay
Abusive behavior that specifically targets gay people is called homophobia.
Generally, if someone calls you gay, and your not gay, they are attempting to insult you because they think that being gay is in insult. These people are homophobes, and usually fear or hate gay people out of ignorance or religious bigotry.
because they like another boy
Because screw you that's why.
The best thing to do would be to call her by her name. But you may call people like her "lesbians."
people who are afraid of gay people, or who just hate gay people, think it's bad to be gay. So they use the word "gay" as an insult, when it's really just part of human nature. Some of these hateful people are actually gay themselves, but can't bring themselves to admit it.