Konnichiwa zeroh4nter-san!
This sentence is difficult to translate because it uses dialects in addition to everyday slang.
The dialect used is Osaka dialect, and is characterized by adding "-や" to the end of words but not "-です".
原文：当ッたり前や！
標準：当たり前です！ or 当然です！
英語：Of course!
I think this sentence is easy to understand.
原文：用兵がどうこうなんざ、空気読んでええ子にしとっただけや。
標準：用兵を論じたりしていたのは、場の空気を読んで良い子を演じていただけです。
英語：I was discussing military tactics and stuff, because I was just reading the mood and acting like a quiet strategist.
Wow, it's a difficult word at first. "どうこう" is "どうのこうの" originally and means "different actions" or "different noises." This word is mainly used in a negative sense.
example
どうこうと、うるさい！
Shut up! (I don't want to hear different opinions!)
This is difficult Japanese to translate into English. But "用兵がどうこう" means "discussing military tactics and stuff" or "discussing military tactics and etc...".
"なんざ" is "などというのは" originally and means "that is to say" or "that is because".
"空気読んで" is "場の空気を読んで" originally and means "reading the mood". However, in Japan, it often means "read between the lines" or "try to anticipate someone's wishes". And passive behavior is preferred over proactive behavior in this case.
For example, in the West, it is considered good to express your opinions clearly. However, in Japan, it is considered bad form to actively express your opinions.
When the atmosphere becomes unpleasant, sometimes Japanese people will remain silent and not express their opinions, even if they are correct. In this case, it is called "空気を読む".
"ええ子" is "良い子" originally and means "good boy" or "good girl". In Japan, quiet children are considered better than active children.
"...しとっただけや" is "...していただけです" originally and means "I was just doing...".
"空気を読んで、ええ子にする" means "Concealing her militant nature and pretending to be a modest intellectual" I think.
原文：こっちがホンマのウチや！
標準：こちらが本当の私です！
英語：This is the real me!
This shows that she is not a tactician who quietly discusses military strategy in the rear, but rather a brave warrior who fights fiercely on the front lines.
As an aside, the historical 張遼 was certainly one of the most powerful generals of his time, but he was also a man of great intelligence and character who was trusted by everyone.
He is particularly skilled at negotiation. He can negotiate with enemies to surrender, and even get along with difficult generals, so everyone has become friends with him.
NANGI
Hope some native or JP experts could tell me what did this character said/mean here. I think this is a slang (not normal JP i learnt at school)
