Yevamos 6:2

Similar to the case in mishna 6:1, if a man has sexual relations with one of the incestuous relationships, or with a woman who is prohibited to him - like a widow is to a High Priest, or a divorcee or a woman who performed chalitzah is to a regular kohein, or like a mamzeres (the product of an incestuous or adulterous relationship) or a Gibeonite is to a regular Jew, or like a regular Jewish woman is to a mamzer or a Gibeonite – in all of these cases, he renders her incapable of marrying a kohein or, if she is the daughter of a kohein, from eating terumah. As in the previous mishna, there is no distinction between relations in a “natural” or “unnatural” orifice.

Yevamos 6:3

(The following scenarios deal with women from kohanic families.) If a widow becomes betrothed to a High Priest, or if a divorcee or a woman who performed chalitzah becomes betrothed to a regular kohein, they may no longer eat terumah from their fathers’ houses (even though they have not yet been married); Rabbi Elazar and Rabbi Shimon permit them to do so. If they were widowed or divorced after being married, they may not eat terumah; if they were widowed or divorced from betrothal, they may.