We know that Rebekah had been accompanied by Deborah when she went to marry Isaac (Gen. 24:59).
Rashi says that it was the nurse whom Rebekah sent to bring Jacob home after Esau’s anger died down (Gen. 27:45), but she died en route. If it is the same Deborah throughout the story, she must have been very old when she died.
Why her burial place was allon bachut is explained by Nachmanides on the basis that Rebekah herself had died and the weeping associated with the oak tree was for Rebekah. But why is Rebekah’s death and funeral not reported more fully?
Perhaps because it was unlikely that the family would have attended her burial. Isaac was old and unable to see; Jacob was away from home; and Esau was impatient with religion (the sages say that his quarrel with Jacob began on the day of Abraham’s funeral, when Esau resented giving up his hunting for the sake of a funeral). So Rebekah’s funeral must have been very modest.