All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There is no harm for your mother to enter the toilet in her home or any other toilet without covering her head as there is no evidence which prohibits this. However, some scholars stated that it is desirable for a person to cover his head when relieving himself, and this applies to both urinating and defecating. Some of them stated that this is a sign of bashfulness and bashfulness is one of the traits of faith, as reported in an authentic narration. Some others scholars argued that covering the hair prevents the smell of urinating or defecating to be absorbed by the hair as the hair is the part of the body which absorbs the smell the most. So if your mother does so in order to obtain the reward of this desirable act, according to the view of those who say that it is desirable, then it is hoped that she will get the reward for doing so.
Allaah Knows best.