Medieval themes include birds as messengers, the power of blood, the dark and dangerous forest, the importance of a virtuous ruler for the natural phenomenon of a kingdom, and chaste love. That last is also a Christian theme, but here it seemed more medieval in expression to me.
And, of course, the story of Snow White is about the nature of Beauty.
The images of Snow White-as-war-leader in the movie are reminiscent of Joan of Arc. With a quick search, this was the best I could find of Snow White:
Here are two images of Joan of Arc from the website Catholic Saint Medals.
Another aspect of the movie is that, while she does wear armor and fight, she is not shown as a great warrior. Rather, she is portrayed as a natural leader: Broken, hopeless warriors who have turned to drunkenness, outlawry, or despair, are redeemed by her innocence and her sense of the mission of redeeming their land and people. With her, they are given new hope and faith. She leads, and with the tremendous power of hope and faithfulness she brings, they fight and die to restore their land and themselves.