For those wondering, Ange is greatly exhausted by this time cause she has been on vigil for a while for any ambush. Which is why her reaction was very slow when the guard attacked Char. Even Ange lampshades this in the LN.
And this is bad writing.
You can't make a manga out of a novel, leave blatant plot holes and hope that people read the novel to fill the gaps.
In many cases, there are enough differences between the two media that the reasons mentioned in the source novel can't apply to the manga adaptation.
(Note that this can work when talking about different supports telling different parts of a story, to some extent. Like Star Wars movies making references to Star Wars TV series and vice-versa. It doesn't work at all in the case of direct adaptations though.)
If fatigue is the cause of her slow reaction, it needs to be depicted
in the manga. Readers of the manga don't need to be told they must go read a different work to get the context. As it stands here, she seemed fine and the priestess was faster than her. It's all inconsistent as the guard was slow enough that a non-combattant reacted fast enough to shield Charlotte but fast enough that a S-rank adventurer known for her speed couldn't react in time. No visible context is justifying this other than LN readers claiming that "the LN makes more sense".
Also, what's the point of being on high alert if you can't react on time when the ambush does come?
By the time she realizes she's too tired to continue, they should have stayed in a safe place. Like the clothes shop.