How about being cheated by her boyfriend C all night?

Don't pay too much attention to this kind of thing. You are not married yet, and you will be together for a long time. If you think so now, you will be very sad in the future. If you really care about this matter, you can tell your boyfriend not to do this to you again. If you are embarrassed to tell him, ask your best friend yourself to see if he really likes you. If he really likes you, you should have a good talk with him and ask him not to do this in the future. I think if your boyfriend really loves you, he won't do such a thing, so you should trust your boyfriend and don't always be suspicious. If you really don't feel at ease, ask him yourself and ask him why he did this to you. If you ask, he says it's his fault, then ignore him. If he says it is your fault, you can apologize to him. If he says it's not yours, then ignore him.