Race points are the only ones relevant for YE#1 at this point and, as it stands today, Halep is
+1546 Kerber
+ 2181 Osaka
+2185 Wozniacki
If Woz wins Beijing, still possible, the points difference will become + 1835. At the time of my post Osaka was still in the tournament as well.
So, there are still 2250 points in play after Beijing. I know Woz and Kerber are not playing any International next week but Osaka does (HK) and in theory, she or any of the other two could play Moscow as well with a WC, especially that Halep withdrew and not sure if her WC was reassigned. I know none of them are in the draw in Moscow, but this could hypothetically change.
Anyway, in a highly unlikely scenario where Osaka or Kerber or Woz wins ALL the points left in play AND Halep withdraws from Singapore or retires in the first match (0 points earned), any one of them could take the YE#1.
My comment was about being theoretically and mathematically possible although the probability is nearly null; this is way I said it will take "a miracle" for that to happen. In other words, I'm saying it's possible but highly unlikely for her to lose YE#1.
Now in a more realistic scenario, if Osaka, Woz, Kerber don't play Moscow (likely) she is indeed YE#1 regardless anything else.