פירוש על קידושין 20:14

According to Ravina, all sages agree that from the Torah, an Israelite woman betrothed to a Kohen may eat terumah immediately. She need not wait for huppah. The issue is whether the rabbis prohibited it. Ben Bag Bag accuses Ben Batera of not being concerned about a “simpon” which is a way of annulling a sale or contract. If the husband can annul the betrothal then it would turn out that she was never betrothed to the Kohen. If she eats terumah before huppah and then the betrothal is annulled it, retroactively it would turn out that she ate terumah as an Israelite.

This is Ravina’s rewrite of Ben Batera’s argument. When a kohen acquires a Canaanite slave, the slave eats terumah immediately and we are not concerned that the sale will be annulled. So why shouldn’t the same be true about a girl betrothed to a Kohen? Ben Batera then admits that the sages do not allow a betrothed girl to eat terumah because of Ulla’s concern that she will feed terumah to her relatives.