The questions of the heart are difficult, if not impossible, to understand. It comes back to understanding what love itself is, how one defines it, and how one expresses it.
Defining the word love is difficult as individual experience and perception play into every aspect of the word. Some define it as an emotion we feel, a synonym for sexual relations, a trap, a manipulation, a sacrifice or a contract. None of these definitions constitute the love that is truth.
My personal experience and perception is that love is a verb. Speaking the words “I love you” is an action of the verb. In essence it is defined as helping when you can, where you can, when asked, and without expectation. Helping is a natural, innate reaction. Seeing a soul struggle and offering assistance is a natural reaction. The love aspect comes in ethically when asking if someone needs love (help), and it declined, the loving aspect is to not push to help; it is allowing the other to make the decision. Love has no expectation; this means no assumptions or expectations are placed on the action. Unconditional love is a standard that is nearly impossible to achieve. It is a goal to strive for.
So in answering the question of how one can love someone and not wish to be with them, though I do not know the experiences of those involved, it can be that their definition is different than yours. Remember though, if you love (asking) and it is declined by the other person, the loving action is to not push but rather allow the other to make the decision. It can be the hardest of all actions – to follow the age old proverb if you love someone, let them go.