I'm also a fan of long hair and agree that when they cut it short it usually doesn't look as good. If they want it shorter for day-to-day actions I'd rather them tail it or put it up or something. I mean, look at Mizuho from Please Teacher (seriously, just look at her. You won't regret it
. Her hair's pretty damn long but when done up it still looks nice without sacrificing the chance at being long again.
As for the translation, I far prefer it to be fluid than accurate. So long as what it's conveying can be enjoyed in the same sense, I'm all for it. To me sideburns sounds awkward, stupid and more like an outright insult than an unwanted nickname.
Calling a girl sideburns is effectivly calling her a hairy lady and that tends to get guys kicked in the nuts.