Okay, user A, exported her own calendar and sent the .ICS file to User B.

User B imported it

This leaves User B with a messed up calendar (it's got like everything of hers AND Person A)

any idea on how to "reverse"/back out the imported, uh, "stuff"?

I always thought it would import as a new calendar, but apparently not (note to self)

All the imported stuff shows up in italics, but I've no idea on how to just delete/remove THAT stuff.