Is it better to not tell someone she's Jewish if she won't follow it?
This is a hypothetical question; it doesn't apply to anyone I know, but I heard an anecdote and it led me to wonder.
Suppose someone discovers that her maternal grandmother was in fact Jewish, but the person's mother never knew this and was raised as a Christian (and passed that on to her children). The person, upon learning of her status, wants to accept it and sets out on that path. This question isn't about her; it's about her mother.
If the person strongly believes that her mother, upon learning of her Jewishness, would not be interested -- would not learn about Judaism, would not give up Christianity, and would not keep the mitzvot -- then should the person tell her mother? Which is worse: for the person to withhold this information, or for the mother to (now) knowingly not follow Judaism?
(In the story I heard, the mother was nearly 90 and the sense was that she wouldn't be willing to make major changes now.)
While this is an unusual situation, it's not novel -- Jews have been forced to hide their identity for safety at some times in our history, and some have abandoned it willingly. There must have been cases where learning about one's true status was not welcome news. What have rabbis advised in this type of situation?