Girls cum just like anyone else, through sexual stimulation of their erogenous zones both internally or physically
While there isn’t a direct indicator of HOW a woman orgasms like you know a man is done when he shoots out jizz but with women, I guess the way they feel, how wet they get, pelvic contractions are different indicators of “how a woman cums”.
There are different types of female orgasms too. Like Gspot orgasm, penetrative orgasm, anal orgasm, nipple orgasm, oral orgasm, clitoral orgasm, a mental orgasm, literally there are so many types of orgasms that if anyone says making a woman cum is hard, they just aren’t focusing on what needs to be focussed on.