These were picked in Chicago in June (1996) and handed to Lady Di by a little girl standing next to me. They're hard to see, but ended up on the cover of People magazine. Thanks for any help!

They look like they could be lily of the valley and that seems to be supported by this article from the Chicago Tribune of 1996

https://www.chicagotribune.com...

" Diana clutched a modest bunch of lilies-of-the-valley as she strolled through the sculpture garden at Northwestern University with President Henry Bienen, who hosted the classy, elite reception afterward."

I agree, Lily of the Valley.