All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Graves must be preserved and one must avoid digging them and harming those buried in them. The people buried in the grave are harmed from the same thing the living people are harmed.
Therefore, you must block the holes that are in your mother’s grave to prevent anything that may harm her, such as dogs and so forth. If you cannot block the holes by yourself, then you may seek the help of others or take the case to the authorities who are expected to do what is necessary to preserve the graveyard and prevent anything that may despise it.
Ibn Hajar al-Haytami said in Tuhfatul-Muhtaaj:
“Yes, if it is feared that a lion would dig the grave, or that flooding would destroy it, then it is not disliked to build it and plaster it; rather, it may be obligatory to do both of them.” [End of quote]
As for the impact of this on your mother in the Hereafter, then there is no effect on her.
Allah knows best.