Is it permissible for a non-hijabi woman to go to the mosque wearing a khimar with regular clothes for the purpose of studying?

Displaying one's adornments (tabarruj) is a danger and a corruption. However, if a woman who displays her adornments desires good and goes to the mosque with the intention of benefiting, and she covers her hair and wears whatever loose clothing she possesses, then it is hoped that this will be a door to good for her and a path to her adherence to Allah's law. As for a disbeliever entering the mosque out of necessity, there is no harm in it, for the Prophet, peace and blessings be upon him, lodged some disbelieving delegations in his mosque.