You might say that you aren’t comfortable staying overnight together–your partner does so anyway.
Some bisexuals have mostly had long-term relationships with men and not as many relationships with women, oftentimes because they were socialized to be straight and pursue boys, so they've just been dating them longer.He or she might say that they are sorry if they hurt you (hit you, scream at you, cheat on you…etc.) and promise that it will never happen again, but their apology is more manipulative than sincere.They might speak badly about a previous partner, claiming that their previous partner was crazy, or a bitch, or an asshole.Therefore others in the LGBTQ community feel it’s important to identify as bi to fight bi erasure, or the common desire to write off the often misunderstood identify. Guys: No, she doesn't want to have a threesome with you just because she's bisexual.
She might want to have a threesome because she likes threesomes in the same way some straight people like threesomes, but assuming she wants that just because she's attracted to more than one gender doesn't even make sense and it makes you sound like a moron. Yes, she's able to commit to same-sex relationships.
Also, please stop trying to do the math on this, seriously. If she likes you, that's all you really need to know.