This is all going to be circumstantial, because a female could be wearing a ring, and it could be attracting the gaze of the non-mahram, and it could not.
The outer hijab of a woman is covering up herself, with the exemption of her face, and her hands up to her wrist. Everything else should be covered.
If she is wearing any jewellery, and that jewellery is on top of her hijab clothing, or on her hand, like a ring, then it could be either halal to show, or haram.
It would depend on whether the piece of jewellery is attracting the gaze of a non-mahram, or resulting in lustful looks, or solely considered as 'zeenah'. In this case it would be haram for her to reveal.
If a woman is wearing a necklace on top of her hijab, or a brooch, a ring, a bracelet, etc, and it is not attracting the gaze of a non-mahram man, then she can wear it.
A woman might not be intending it to bring notice of a non-mahram, but it would still be considered haram if it is bringing notice, as it would be considered as zeenah.
And Allah knows best.