I think I figured out the confusion with the two photos. When Victoria died, the Court went into full mourning for a year. After that, there was half mourning, ending before the original date for Edward's Coronation. Edward and Alexandra attended their first State Opening of Parliament in February 1901. That's the top photo where Alexandra's dress is fairly plain, she has a black veil, and she's not wearing *quite* so many jewels.

The second photo is of the State Opening of Parliament in January 1902, right after the Court ended full mourning and went into half mourning. That's why Alexandra is wearing a lot more jewels, her veil is white, and her dress is more glamorous.

I'm pretty sure I'm right about this...