Ok, let's take Kathleen O'Neal Gear and Michael Gear's as source.
What would shield maiden have looked like, if they really existed?
“There were once women in Denmark who dressed themselves to look like men and spent almost every minute cultivating soldiers’ skills. …They courted military celebrity so earnestly that you would have guessed they had unsexed themselves. Those especially who had forceful personalities or were tall and elegant embarked on this way of life. As if they were forgetful of their true selves they put toughness before allure, aimed at conflicts instead of kisses, tasted blood, not lips, sought the clash of arms rather than the arm’s embrace, fitted to weapons hands which should have been weaving, desired not the couch but the kill…”
For me this is not the description for Lagertha from Vikings, for me it's more like Iceborg from fifth element: