I think they knew that everyone wanted this romance as male V, like come on they advertised her and hyped people so much, I'm pretty sure that they have dialogue lines prepared so I guess it's no problem for them to make her bisexual, they could come up with something like "I'm not lucky with women, maybe it's time for something else", change sex scene a little and that would be enough. I think that Panam should also be bisexual because these two actually change the ending. Overall, romances in game are very disappointing, they seem cut. So we have to wait and believe that something will change either with the free dlc or in the upcoming big updates in January and February. For example, in one of patches for Witcher 3 they actually added some new romance options for Yennefer and Triss because community wanted this so yeah, we must hope.