While she did look rather cute, I decided it may be best if we got it back behind both ears. Leading may be a bit easier that way, and I sure didn't want to get up the next morning to find she'd rubbed it off the other ear as well!
Getting the halter back on took several minutes as she's decided she's not terribly fond of brushing (at least not today) and didn't want to stand still. I did find that my hand worked better than the curry, though, as I could reach over and scratch just beneath her mane on the off side, which is also the side the halter had been pushed over the ear on. Eventually she allowed me to scratch around her ears, and from there it was pretty simple to just pull the halter back into place.
She's not convinced that the rest of the girls aren't going with the off the ear look, however, so I may find myself battling this one. Two year old fillies seem to have the mentality of teen age girls :)