What is the ruling on looking at a modest woman who is covered with an abaya, and is it forbidden? And does she have the right to prevent me from looking at her?

It is impermissible for a man to freely gaze upon a non-mahram (definition) woman, as this is a gateway to tribulation (fitna) and corruption. He must avert his gaze from her, based on the Prophet's (peace and blessings be upon him) saying to Ali: "O Ali, do not follow a glance with another glance, for the first is permissible for you, but the second is not." And his saying to Jarir regarding an accidental glance: "Avert your gaze." The fact that a woman is modestly dressed does not permit gazing at her, even if she wears a niqab, because "how many daggers are there in the eyelids." And because lowering the gaze is obligatory from anything that one fears will cause tribulation. It is not permissible to follow a woman with one's eyes, even if nothing forbidden is seen from her, as a preventive measure (sadd ad-dhara'i') and to ward off tribulation. If it is forbidden to look at a woman, then she has the right to object to a man looking at her.