Because that is how Arian coded it.How come she won't romance a female CHARNAME without a happy patch or messing with globals, then? If a female can only get so far in the love talks before they stop... why not just continue them for the female? Then folks who hack the romance with a female PC don't get stuck with male pronouns at the end.
If people want to change the game on their machine, that is their choice. The original intention of the first creator will be kept, which is why when I go to editing I will remove all the various action dialogues on the lovetalks, and make it conform to the original.