2016-12-23: Various Ways to Spend Christmas Eve Eve

[Mamorien]

there's nothing wrong with the story, but I have absolutely no clue who these 4 are or what Source they are from.  I'm guessing an anime, possibly a manga. But that's just based on them being Japanese schoolgirls.

You're guessing right. They're the main characters from a slice-of-life 4koma called Lucky Star, which (as per the footnotes) did indeed get an anime adaptation. Now you know, and knowing is half the Mandatory Educational Content segment.