As to your options, I suggest a third:

(c) Wotan glance and the men and Sieglinde are discrete. He looks at the men and then he looks at her. But the glance itself is the same. That is, they are two different tokens of the same type. Thus the glances are objectively the same, but they are received differently by the men and Sieglinde. They are base mortals who are terrified at the glance from the god, even when his divinity is otherwise veiled. But Sieglinde has Wotan’s blood flowing in her veins and recognizes a kinship instantly. And because of this kinship saw past the terrible appearance and discerned something deeper.

This is paralleled in the twins coming to recognize each other. Siegmund is rejected wherever he goes, but Sieglinde recognized something kindred in him almost as soon as she first discovered him in the lodge. (Dich grüsste mein Herz mit heiligem Graun, als dein Blick zuerst mir erblühte / My heart greeted you with sacred terror, when your glance first bloomed on me.) Siegmund says the same thing about radiant light from the sword in the tree (Wie der Schein so hehr das Herz mir sangt! Ist es der Blick der blühenden Frau, den dort haftend sie hinter sich liess, als aus dem Saal sie schied?)

The light from the eyes is the same in all cases. To mortals it is terrifying when it comes form a god or disagreeable when it comes from their human offspring. To those with a spark of divinity it is altogether different.

Getting back to Wotan and Sieglinde, an interesting question is whether the “sweet longing sorrow, tears, and comfort” is her own or Wotan’s. In other words, are his eyes like a mirror into her own soul or into his? Here again I think the answer is both. She reads he soul, but in reading his reads her own.

If this is correct, Sieglinde actually has insight into Wotan’s suffering and hope even before he does. For when he appears in the next act he is all jubilation about his two plans. It is only when Fricka unmasks him that he realizes his true despair. And only after witnessing Brünnhilde’s rejection of Valhalla does he see his true hope. For Wagner, Woman intuits the true state of Man.

But more on this later.

In favor of (b):

The translation above seems not quite right. The text says, “mir allein weckte das Auge süß sehnenden Harm, Tränen und Trost zugleich” which I would give as “to me alone his eye awakened at once sweetly longing sorrow, tears, and comfort.” Thus, the emphasis is on what was awakened within Sieglinde by Wotan’s glance, not a description of the glance or of Wotan himself.

In favor of (a), the next stanza says, “he glanced at me, and flashed at them” (auf mich blickt er, und blitzte auf Jene), which would seem to imply two different ways of looking.

However, (i) this could be a figure of speech, by which a subjectively different response is indicated by objective description; (ii) the phrase is qualified, “after he brandished a sword in his hands” (als ein Schwert in Händen er schwang); thus, it could be that at the new episode of producing the sword, the eyes did have two different “looks,” without implying that this was so in the earlier glance.