She's not afraid, but she certainly is disgusted. Try preparing a meal for her and then watch her spit out every mouthful into a bowl, see how honored and appreciated you feel then. So it goes here. She doesn't want her man, and this is her way of letting him know what she REALLY thinks of him and his sexual desire for her.
If she’s not going to swallow my semen, I’d rather spill it all into my own damn hand and eat it myself. And for that, I might as well make things easier and jerk off to porn or to anime chicks.