I guess the reason there were two tags is that this woman doesn't know how to spell your sister's name.
Honestly, I would just never accept someone's request to tag *my* pics. If I don't want to tag them, and they're not *you*, then I don't want you to tag them at all.
If I chose not to tag you (preserving your privacy), and you wanted to tag yourself so people could see them, I'd accept.
But I would never let Person A tag one of *my* photos w/ Person B's name. Honestly, I think that is rude.
And maybe you should have dropped her an e-mail that said, "I took your tags off after all bcs you misspelled my sister's name--her name is properly spelled S-u-s-a-n J-o-n-e-s; you might want to update your address book."
In other words, notified her, the way she notified you. But honestly, I don't think it's horrible that you didn't.
And maybe she doesn't understand why it's unnecessary to tag someone in that situation.
(is she creating an alternate identity for herself, using a misspelling of your sister's name, but all sorts of *other* details about your sister? Maybe see if Facebook has an entry for that misspelling?