Praise be to Allah.
There is no difference of opinion among the scholars concerning the fact that the Prophet (blessings and peace of Allah be upon him) stoned the jamaraat with seven pebbles (each). This was his practice, beyond a doubt.
Ibn al-Qayyim (may Allah have mercy on him) said:
It is narrated in saheeh reports from the Messenger of Allah (blessings and peace of Allah be upon him) that he stoned each Jamrah with seven pebbles. This was reported by ‘Abdullah ibn ‘Abbaas, Jaabir ibn ‘Abdullah, and ‘Abdullah ibn ‘Umar. End quote.
Haashiyat Ibn al-Qayyim ‘ala Mukhtasar Sunan Abi Dawood (5/31 2)
The scholars differed a great deal concerning the ruling on one who falls short in the number of pebbles used in stoning the Jamaraat during Hajj. There is no text concerning this matter to which reference may be made in order to resolve the difference of opinion.
It says in al-Mawsoo‘ah al-Fiqhiyyah (17/80, 81):
The view of the Shaafa‘is and Hanbalis is that the one who does not stone the Jamaraat at all, or omits to do so on one or two days, or omits three pebbles in the stoning of any one Jamrah, must offer a compensatory sacrifice.
According to the Shaafa‘is, if anyone is short of one pebble, he must give one mudd in charity, and if he is short of two pebbles, he must give double that amount.
According to the Hanbalis, there are several reports concerning one who is short of one or two pebbles.
It says in al-Mughni:
What appears to be the case is that Ahmad’s view is that he does not have to do anything with regard to being short of one or two pebbles.
The Hanafis are of the view that a compensatory sacrifice must be offered if the pilgrim fails to stone all the Jamaraats on the four days, or if he omits the stoning for an entire day. The same applies if someone is short of most of the pebbles on one day, because it that case it is as if he did not stone the Jamaraat at all, so a compensatory sacrifice must be offered for that.
But if he omits a few pebbles on one day, then he must offer charity, giving half a saa‘ of wheat, or a saa‘ of dates or barley, for each pebble he omitted.
The view of the Maalikis is that he must offer a compensatory sacrifice for omitting a pebble or for omitting all of the pebbles. End quote.
What appears to us to be the case – and Allah knows best – is that if she is certain that she omitted three or more pebbles from one Jamrah, then she must appoint someone to sacrifice a sheep on her behalf in Makkah and distribute its meat to the poor of the Haram. If she is not certain about that, then she does not have to do anything.
And Allah knows best.