I think Alex is upset because Cole never speaks his mind... He asks Cole about his feelings, his interest, where does he want to go, but Cole responds nothing or I don't know or wherever it's fine... Even if Alex asked Cole about the bet I belive Alex thinks Cole wouldn't be honest anyway... Also Alex is upset because he knows Cole doesn't trust him.
The girl doesn't seem serious about Alex to me, she seems to be just playing for no reason, maybe she is curious about how strong is their bond... (I know she tried to seduce Alex but she didn't insisted when he said he wasn't interested... she doesn't seem to dislike Cole or be jealous either... she is weird xd)
Also the gun stuff is pretty messed up... I mean I would be scared if someone went all psyco because he thinks I amm cheating when I am not... But Alex seems also angry... I think he is offended because Cole says he loves him but still doesn't make an effort to communicate with him, doesn't rely on him as a boyfriend when he ofers to listen...
I agree that Alex might be feeling a bit upset overall with Cole for not speeking out more, but it didn't really show that much. Besides, you might say that not having any preference as to where to go meant that Cole was saying he was happy as long as he was with Alex. I would also say, that there's no way you can know that Alex didn't ask Cole about the bet just because Alex thought Cole wouldn't be honest. In fact why would he think that? Nor is it clear if Alex is still getting upset over Cole's lack of trust in his preference at this point, but if he's aware of it he should realize how things might appear to Cole that morning and reasure him.
As to the girl, her behavior if not intentional is then more than wierd. Do you ramdomly mess with a strange couple you just met on a beach, lying to both separately, knowing full well that they may break up over it? Just for kicks? Or like some self proclaimed cupid see it as your mission to "test love bonds" uninvited? Most women have the decency to back off when their advances clearly aren't welcome, and look elsewhere. She may not dislike Cole, but she certainly is not being nice to him either, more like mean, insensitive, and callous in the extreme.
Well I am not defending her... I think everything she did and said was inmoral... I was just trying to point out that I don't understand her motives at all.. she seems like she's just toying with them..
Also I have not idea why Alex hasn't asked Cole about the bet... I was expressing a possible explaination, but I am not sure.... Also if they were real people this relationship would be even more confusing and complicated because people often behave irrationally and contradict themselves when romantic love, insecurity,and obssession are involved
;) I think it's a problem all of us have when reading any sort of fiction, when the author chooses to leave a character's motives and thoughts vague it is all too easy to read our own initial impression into it, and sometimes far more than we should. Often we tend to read into it what we want to it to be, not what there is evidence for. But I did realize that you were only expressing an opinion. What I stated rather badly in return was was we did know was that Alex didn't ask, but could say nothing as to why.
I would also think that Cole's issues on communicating his feelings and preferences as to where to go is not the same thing as not telling the truth if asked about a bet. Indeed, Cole usually admits the truth when Alex confronts him. The only reason for Alex not to ask would be if he believed it of Cole, and either didn't want to hear him admit it or wouldn't believe a denial.
But you're right, people IRL behave with same irrational ways, and people will also assume too much as well. Sometimes it is a good thing to keep in mind just what it is what we do know and that there can be more than one possible explanation.
As to that girl, I really hope she wasn't just a mere plot device of a moment to cause trouble between our boys. Her actions would be so nonsensical in that case. So I hope she had some reason and intention with what she was doing. Which would also mean that we will see her again.

I think the that girl just played both of them. She told Alex that she and Cole had made some kind of bet, which I bet (hehe) was untrue, and then probably equally untruthfully implied to Cole that she and Alex slept together. It would seem that she is intentionally trying to break them up, and the question remains as to why.
As to the gun, as so many have already pointed out, Cole had it in ch. 4. But it is a bit drastic, even if he does believe that Alex cheated on him and is now somewhat ignoring him. But then Alex never did ask him about any bets he might have made and was ready to suspect the worst, just because some girl said so, and let it get to him. And Alex, unlike Cole, doesn't suffer from inferiority and lack of confidence issues.