Why won't the family let Ruth see her mother when she is in the hospital in chapter 21 in "The Color of Water"?

The Color of Water is a memoir about
a family comprised of two distinct and relatively segregated cultures. Ruth, the
author's mother, was raised as on Orthodox Jew. Her family kept the Sabbath traditions
and rituals faithfully, were educated in Jewish schul as well as
public school, and ate kosher. Her parents wanted her to marry a Jewish boy, and her
father went to great pains to set her up with anyone Jewish (much to Ruth's dismay).
Instead, she chose to leave home and marry a black
man.

Once Ruth does this, she is dead to her family. When
Ruth asks to visit her dying mother in chapter 21 of the novel, she is told the family
has sat shiva for her--the Jewish rite of mourning. It involves
praying, turning mirrors down, covering their heads, and sitting on boxes for seven
days. While she is not actually dead, once they sit shivafor her,
she is dead to them. That means Ruth cannot come visit her mother, even though her Mameh
is dying.