How you transmit when a girl is have a sexually feeling(horny)?

it always comes to be when iam surrounded by health class how can you describe a girl is horny ?? hmm does the chest grow bigger when she is like sexual premonition?? Uhm No. She may be a little shaking. And reaction her down there to check if lubricating through pant.
i only bearing you can really tell is if she is drizzly.