Short answer: BAIL NOW!!!!
Long answer: I fucked whores in three different countries (the US Mexico and Brazil not to mention countless strippers) and I will tell you now I'd marry any of them before I'd marry a girl involved in threesomes. Reason being any girl involved in threesomes is doing so by choice, not for money, not for survival, simply because she's a filthy slut. It just gives you an insight into her personality and thought process. For example if during any of those three-somes, do you really think she would've protested if a fourth, fifth, or even six guy entered the room?!? So when all out gangbang is definitely in her disposition not to mention it probably wouldn't take much to get her to do things with a farm animal, separate yourself from that filthy whore as soon as possible.