Maybe this look
Rogue from X-Men (Anna Paquin).
As far as I can tell, in the case of Stacy it’s natural-she’s had the streak since age 12:
Sometimes this is caused by a birth mark on the scalp or other skin disorder like vitiligo, where the pigmentation of the hair shafts prematurely ceases; it produces this ‘look’. One local news anchor also has this – Colleen Williams of KNBC-4 Channel 4 news. I noticed this some years back, and while it makes for an interesting ‘fashion statement’, I think in both their cases it’s actually naturally like that.