I don't know how other people feel about this, but by all respect for the need to create a "dramatic" situation at the very beginning of this novel and for the way that situation was created and developed, that situation was in fact artificial, had not much to do with reality! On my book a lesbian relationship of my girl with another girl is NOT CHEATING!
I used to be very jealous as I was young but I would have never seen a lesbian relationship of my girl as cheating or as a threat for me. Coz there's no other DICK involved! And it is NOT MY PLACE in the heart of the girl that is taken by another girl either. A BI sexual girl can love a girl AND a man at the same time, because these are different parts of her persona. They are not "either/or" by nature! There is no "competition" in her heart between a man and a woman. They can naturally coexist!
I would have never had the denial reaction that the MC had when he found out that both girls he dates and kinda loves also date and kinda love each other. My reaction in that moment would have been in fact: YAHOOOOO, i'm a fuckin' lucky bastard! Very much like Derek's reaction when he first heard it
In fact, for me this "combination" would have been PERFECT!
And the same goes for each of the 2 girls, if they are both really BI sexual (which I bet they both are, even if Maya may need some more time to agree to that fact). Their love for each other is one thing and their love for a man is another (and the fact that it's the SAME man makes things even nicer). There should be no conflict here and no need to chose one over the other. Feelings for a man and feelings for a woman do not compete, they co-exist in a BI sexual person!
As for the MC, which man in his right mind would prefer to have only ONE woman when he could have TWO? Comeon now.. really! And if all 3 participants in such a relationship are able and willing to accept the truth about it and if all have the strong wish to take care about this special relationship among them and to develop it, then it can really become PERFECT for all!