Some sisters, Shaykh Salih, are truly shy to ask about such matters, and months may pass before they ask.

She should seek understanding in this. Matters of religion are not something to be shy about, and Allah is not shy of the truth.

So shyness should not prevent her from asking about her religion.

The sahabiyyat, may Allah be pleased with them, used to ask the Messenger ﷺ about menstruation and matters of their religion, and they were not shy about it.

Yes.