The 24-year-old flanker's powerful running saw her storm over the whitewash either side of half-time, and added to scores from Lauren Cattell and skipper Sarah Hunter were enough to see the Red Rose to a 32-0 win.
It was the perfect start to the 2016 Championship for Bemand's side, who came into the clash with a point to prove after their worst-ever finish last term.
Having lost both of their away games in 2015, England never looked like extending that record as they took the game to their hosts from the outset, and Bemand was impressed with impact of player-of-the-match Millar-Mills.
"Harriet has been bubbling away beneath the surface for a while now," he said. "She's really grasped the bull by the horns this time and has got herself in peak physical condition.
"She is playing like this every week for her club, so it is not a surprise that she's got that level of performance in her. It's great for her to be able to show her running game on this stage, particularly in conditions like this, and hopefully there's more to come.
"This was our first game in this year's competition and I think that had the feel of a first game about it.
"But we've come a long way, played in wet conditions, and got exactly what we wanted which was a win. To do that in Scotland and to not concede any points is something we're very proud of.
"Last year was last year, and we've made no bones about saying that we are very keen to move on from those performances.
"Scotland turned up to try and play and the most pleasing thing was our energy in defence to shut out a very spirited Scotland team. It was a good contest but we got what we came for."
