Yevamot 87 - Marriages, births, deaths
A Jewish woman who marries a Kohen becomes part of his family and, since she is his "acquisition" as a wife, can eat the priest's portion of the crop, or "terumah." Let's look at the possible metamorphoses that she can later go through.
If her husband the Kohen dies, but she has a child from him, she can continue to eat terumah, as if her husband was still alive. If she then marries a Levi, she may eat Levi's due from the crop - that is, first tithe ("maasar") but she can't eat terumah any longer.
Here was can note that the author of this ruling is Rabbi Meir, who forbids the first tithe to a non-Levi.
If her husband the Levi dies but she has a child from him, she can still eat maaser. If then she marries a regular Israel, she may not eat either maaser or terumah. If her husband the Israel dies but she has a child from him, she still cannot eat either maaser or terumah.
If her son from the Israel dies, she can again eat maaser, on the account of her child who is a Levi. If her son from a Levi dies, she can now eat terumah, because of her son who is a Kohen. And if that son dies, she again cannot eat either maaser or terumah.
Art: Portrait of the Artist's Wife by Tadeusz Pruszkowski