If you claim Helayna, Alexia will always move out of your room with a hit to her affection, the exact amount depending on your response in the conversation where she moves out.Do you have to choose between Helayna and Alexia or can you make it work with both? And if so how?
But this doesn't end your relationship in any way. It alters some lines/scenes, but I don't think it even locks any scenes off. So yes, you absolutely can make it work with both thus far, though not with any real resolution of Alexia making peace with the situation or anything. That said, given Alexia has a threesome scene with Liurial and an entire series of scenes for Helayna involves her getting off on seeing you with others, one assumes at some point there will be a resolution there involving Alexia and Helayna...making up, and I may die in happiness if it comes.