Sabarimala shrine was closed to women of “menstruating age” – defined as between 10 and 50 – until India’s top court overturned the ban in September.
Kanaka Durga and Bindu Ammini, 40, made history after they entered Sabarimala in the middle of the night escorted by policemen.
But as news of their entry spread, violent protests carried out by Hindutva forces across the southern state of Kerala, where the temple is located.
The two women were then made go into hiding and kept moving locations under police protection.
Bindu Ammini said that although Kanaka Durga’s husband initially opposed her decision to enter the temple, he later changed his mind.
Kanaka Durga “was hit on her head by her mother-in-law when she returned home on Tuesday morning”, Ms Ammini told BBC Hindi.
Friends say her family did not support her decision to enter the temple and felt she had insulted their beliefs by doing so.
“They did not want her to return home because they believed she had tarnished their name. Her community too was opposed to women entering the temple,” said Prasad Amore.
A police official told AFP news agency that Kanaka Durga has registered a case against her mother-in-law, who she alleges beat her with a wooden stick, including on her head.
The severity of her injuries remains unclear.