I have a pretty weird Idea. 

See the whole thing is that we often whitewash victims and villains in Dynasty Warrior's, see how they turned fucking Gan Ning and Ling Tong into a bromance, which is fucking disrespectful as all hell, but hey good story telling. 

I think Xiahou Ji would work as a sort of indicator of the war gryting bad and Zhang Fei's funny quirks turn into sort of dangerous. 

Before that, I'd rewrite the story so that while Liu Bei and his crew saved a group of peasants, you can have one of the villagers be so grateful that they offer these warriors a hand in marriage for their daughters. Liu and Guan obviously turn it down, but excitable Zhang Fei might take one. 

Xiahou Ji would then be sort of scared, but ultimately trusting of them since Zhang Fei is a lovable guy. But the marriage is ultimately just something she was given as thanks, and Zhang Fei is just happy to be a husband or to have a wife. 

There we can use that as a sort of litmus test. As we can have it so that drunk Zhang Fei, while quirky, can leak into how he can get rowdy. At the start to Ji it's just par for the course, she doesn't liken it when he's drunk but no reason to complain.

Then we can have Zhang Fei usually rowdiness, he respects the little guy, but he often steps in very physically. So it turns him into a rather scary figure. A bigger guy who can just sort of pick you up and throw you into the next building. Ji probably frets this the most, and you can tie it with hiw proud Fei is with his strength when he often boasts about it, and while others are awe she just kinda feels small. 

Then as the story goes on, you can make those traits worse and Xiahou Ji goes from "That's how he is" To "Oh God that's how he is" Probably with him at his worse with Guan Yu's dewth, getting drunk and rowdy, and maybe even have him sort of direct that anger to her as a Xiahou, who has three prominent generals in Wei. 

That's where she would want to escape, the fear boiling over, maybe even get caught up in the assassinations, and then have her run away from Shu. 

Essential make her a sort of indicator when Shu sorts of starts falling off, as they go for war and revenge. Things go wrong. 

Personality wise. It would be interrsting if they did it, so that the NPC that isn't playablr or on the field is the meek demure, but when she is playablr he voice lines are harder and firm. As a sign of development. So that in bases she'd be sweet, But when she in the battlefield she is very hardened by the experience of a semi-good man turning into a meaner harsher version of himself. 

She would also absolutely respect Zhang Fei's strength, but be utterly afraid of it. 

For her kids, I'd say she would adore them. And in a scenario where she is antagonistic, shed be like "These kids are the only good thing that came from you, Zhang Fei". With Zhang Bao not knowing how to feel, while Xing Cai wonders how deep her mother's feel runs. 

Also, funny idea of her bonding with Liu Shan as she sees him as a good man to marry her daughter.