I'll do you one better:
Spoiler
Also, random image I wanted to post (warning - huge):
Spoiler
Dat face
Re: Magic/Curses - I would say that the issue is partly that Twilight has a specific and picky terminology when it comes to magic, but I think this makes sense considering she's studied it extensively and it is treated along the lines of 'arcane science' (the way magic is also treated for D&D wizards) rather than some dark pact (like Pathfinder witches) in the show. I also think Twilight is making a blanket statement here and is trying to defend Zecora, so she may not be striving for supreme technical accuracy either.