There is a lot of good drama/comedy in that little conundrum. Sometimes referred to as a Bizarre Love Triangle, after the New Order song.
Even if the writer chooses to challenge that assumption, there will be some pretty tricky footwork required to make it all come out to a resolution. It can involve as many people as you like, turning it into a square, pentagon or more, but ultimately the love remains unrequited. Alice wants Bob, who is already in a relationship with Claire. Alice might try persuading Bob to give up on Claire.
It has been telecast every year since 1964, making it the longest running Christmas TV special in history.Since then, stockpiles have been reduced somewhat, but in the big picture it is mostly irrelevant. If anything, the world is more dangerous today as apparently radical nations add their own nuclear weapons to the world’s nuclear arsenal. Alice wants Bob, Bob wants Claire, and Claire wants Alice.Bob is unaware/neutral (leaving Alice as a Hopeless Suitor), or is aware of the interest and can't/won't reciprocate (leaving Alice in the "friend zone"). If Alice is Axe-Crazy (or otherwise extremely jealous), she might attempt to Murder the Hypotenuse.