Ketubot, Chapter Eleven, Mishnah One
This mishnah and the following mishnah deal with the rights of a widow to continue to live on her husbands estate.
A widow is to be maintained out of the estate of [her husband’s] orphans [and], her handiwork belongs to them but it is not their obligation to bury her.
Her heirs, who inherit her ketubah, are obligated to bury her.
In mishnah 4:12 we learned that one of the stipulations written into every womans ketubah is that if she becomes a widow she may continue to reside on her husbands estate and be supported by the inheritance that he left for his children (be they her children or not). Our mishnah adds that since these heirs are supporting her, any handiwork that she produces belongs to them. This is the same arrangement that would have existed while her husband was alive; she received guaranteed support and in return anything she made belonged to him.
However, unlike her husband who was obligated to pay for her burial, the heirs who are supporting the widow are not obligated to do so. The difference is that these heirs will not (necessarily) inherit from her, whereas her husband did inherit from her. Her heirs (either her father or her children from another marriage) are responsible for her burial. The underlying reasoning behind this makes some sense; the person who will benefit financially from the estate of the deceased is responsible for the burial.