The Rabbi [author of] Beit Oved wrote on the halakhic rules concerning Hanukkah … that those who inherit are obligated to provide the widow with oil for Hanukkah to light each and every night, and are obligated to provide all requirements for commandments that have physical requirements…
It seems to me that since it is the custom to increase [lights] each night, as the Rabbi of the Shulchan Aruch wrote, and we have not heard that in our day "one light for each person and their household" [applies] but rather that people all add [a light] every night, that although inheritors are not obligated by law to provide more that the oil for a single light for each night, they are obligated to do so because of the custom in any case, and must give her oil so that she may add [a light] each night. Since it was the custom her entire life with her husband to add a light, even if she renounces before the inheritors and agrees to light a single light each night, she may not ignore the custom. All the more so if she does not wish to ignore the custom.