Edelweiss:
For the love story, maybe it's a Japanese localized variation of the story about how a youth would pick an Edelweiss (a flower really hard to get to, but which will thrive in such a harsh environment) to show their willingness to go through immense efforts for their love (which hopefully will thrive just as well as the flower).
For the "from an angel" - the Edelweiss has often been used as a lucky charm just because it's pretty, hardy, and difficult to get hold on. (There are many stories about how climbers would have died in the hunt for an Edelweiss, whether it be for luck or love.)
-But for the love story, most likely it's about another flower. Remember that it could be a case for an "unreliable narrator" (i.e. either the mangaka is wrong - or the romantically interested onlooker is wrong)
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Either way, thank you for your hard work.