Is it absolutely forbidden to apply artificial eyelashes, or is it permissible if not applied permanently for a specific occasion, such as a wedding, or with the husband's approval for a married woman, bearing in mind that the hadiths prohibiting hair extensions pertained to head hair?

There is no difference between a married woman and others regarding the ruling on eyelashes. The ruling on wearing them temporarily or permanently has been detailed previously. There is no difference in the prohibited extension, whether it is for the head, eyebrows, or eyelashes, because the Prophet, peace and blessings be upon him, "cursed the one who applies hair extensions and the one to whom they are applied." This is inclusive of all, and the consideration is the generality of the wording, not the specificity of the cause.