Praise be to Allah.
Because this crowding is inevitable on days like the twelfth (of Dhu’l-Hijjah), and people may want to hasten (to leave Mina), and it is not possible for them to delay it until the crowds become less, then there is nothing wrong with the woman appointing a proxy. In fact it may be essential for her to appoint a proxy in a situation such as this, because joining the crowd will undoubtedly pose a danger to her.
But on other days, it is possible to delay stoning the Jamaraat until the end of the night, and it will be easier. End quote.