Is it permissible to register on a website to offer advice and discuss Islam with non-Muslims without the parents' knowledge, given an incomplete study of Sharia and reliance on trusted websites for answers?

The default ruling for women's participation in online forums is permissible if it serves a beneficial purpose, such as proselytization (da'wah), giving advice, or introducing Islam, and if it does not lead to any religiously prohibited outcome. Similarly, a woman's dialogue with men online is permissible, provided it adheres to the শরعي guidelines.

However, the temptation associated with women is great, and it is preferable for her to limit her dialogue to other women. As for doing so without her father's knowledge, there is no sin in it, unless the father forbids her for a valid reason.

It is incumbent upon a knowledgeable student of Islamic law, who is capable of refuting misconceptions, to undertake the task of inviting non-Muslims to Islam.