Twilight and Rarity should have split this pot (at least up to Twilight's bet), but it was awarded entirely to Rarity. There are frequently cases of the pot being incorrectly distributed. For example, when one person goes all in, and another person wins the hand, second-placers seem to get some of their money back.
In general, when one person goes all in, the win / tie detection can be completely off.
I just got another example, where there was a set in the community, and I had a king + 5 in my hand and won against an opponent who had a king + queen in her hand. (None of the cards on the table were as high as a queen, so set + king + queen should have won outright.) The opponent in question had gone all in, but she didn't even get a portion of the pot back.
