I don't know, and nobody but Xi Jinping knows.
There is a race going on, between the severe strokes of bad fortune that have hit the Chinese supreme leader (I had written something else and then substituted this), and the iron grip that he has on the state. If the dissatisfaction of his people goes below a certain point, he will lose his position. If he wishes to attack Taiwan, he will have to do that before his acceptability with his own people goes below that level. A lot of speculation is going around about the possibilities of invasion, and about the timing, and the fact is, nobody outside the Chinese politburo, if even they, knows.
If the Taiwanese elections don't go their way, their anxiety will rise, but so will the confidence of the western powers that they are doing the right thing backing taiwan.
If your sister can avoid being in Taiwan around the time the elections end, for a month or two, that would probably be wise.
Better safe than sorry.