Hi, Beth. I'm a left-handed calligrapher and I've taught lefties too. The absolute BEST thing to do is leave them alone. Lefties are famous for learning it backwards, etc. and it's a "built-in" thing that all lefties have acquired since they had a rattle put into their right hand. Just as "righties" find their own style of calligraphic writing, so will the "lefties". You won't need to buy diff. nibs or pens or cut anything different. Some lefties will automatically turn their paper, some will cock their wrists...all the things lefties do when they do normal writing. I've personally tried the left-handed pens and nibs and find them more of a problem than the regular pens.
You are so right. I'm a lefty and somehow I figured out how to do calligraphy using all the right-handed tools. I can't use left handed scissors either.