Brunhilde is awarded for earning 150 reputation on each of three different sites (other than SO). I've earned the hat on four sites so far, three initially and the fourth today when I crossed that reputation threshold. So it appears that the hat isn't a one-time award; once you have it, other sites get added when you meet the requirement there.
As of today I've earned 165 reputation during Winter Bash on Mi Yodeya (or 167 if the +2 for accepting an answer counts). However, during that time a user was deleted, costing me 20 rep. It's been more than an hour since the last rep increase, which is longer than it usually takes for hats to show up, and I have not received the hat.
Is this expected behavior? Is the hat really for a net increase of 150, as opposed to earning 150?