Are 你 serious? That's wrong on so many levels. You're gonna just break up with your boyfriend just because somebody else asked 你 out. That's messed up. 你 figure out what 你 need to do. I'm not helping 你 with your soap opera shit.
Umm no! What kind of girlfriend are you?! To been consider breaking up with a man for his own friend! that is so shallow and rude. Not only will it wreck your relationship with guy one but did 你 even consider what it'd do to their friendship. Gosh if I were him I'd end it with 你 here and now!
Have 你 ever thought about breaking up with Dom before this? Was it because of other boys? What kind of person is Tyran and would he make a good boyfriend? (I'm going to assume not. What kind of person asks out their best friend's girlfriend?) Are 你 happy with Dom? If 你 have to even ask this question, I doubt your relationship with Dom is very strong.
But only 你 can answer this question. Think about how each boy means to you. Good luck.
Also, I would recomend asking for 建议 at link 下一个 time. People at this spot tend to be a bit harsh. ;]