3 vs 1?! That's basically a death wish. There are a lot of times where they could've taken advantage of the haymaker swings of the girl! She's basically open every time she swings that halberd looking thing, "Hey! Hit me here!" is what she's saying. They also could've gone behind her, WHERE SHE'S OPEN! Even if she does attack from her rear— she's exposing her back to the other knights who want to hurt her.
Also, you can't be athletic while wearing armour; jumping? sprinting? front flip? Yeah, you can't do that with armour on, IT'S HEAVY AF!
Am I reading too much into this?! YES! I just forgot that this is a manga, and real-life physics don't work. But I'm still on the 1st chapter ... so maybe it will get better???