how on Earth can the subjective probability be different from the correct betting odds?!

Because the number of bets she makes will be different in one outcome than the other. it's exactly like the bookie software bug example I gave. Normally you don't need to think about this, but when you begin manipulating the multiplicity of the bettors, you do.

Let's take it to extremes to clarify what the real dependencies are. Instead of waking Bea 2 times, we wake her 1000 times in the event of a tails flip (I didn't say 3^^^3 so we wouldn't get boggled by logistics).

Now, how surprised should she be in the event of a heads flip? Astonished? Not that astonished? Equanimous? I'm going with Equanimous.