Not to degrade her character, but outside of doing the do with kazuya and being a focus for jin's rage. she's kind of irrelevant? Both jin and kazuya have evovled as characters post her death, along with that kazumi's an heihachi's thing seem way more relevant to thosw two how they are who they are as people. Jin's found someone who fills his heart with good things, and kazuya is about to move on with his life, the old fashioned way.
not for nothing but, I think this is a situation where you may have liked a character, that they were planning to use for an important story bit a long ass time ago. And they changed the story, and just never got around to it. Both kazuya's and Jin's stories could just fuction with kazuya dealing with his mom and jin confiding in Xaoi , which the latter way more interesting.
She's kind of not needed anymore.
It happens a lot, they start up a storyline in something come up with a better solution, and don't really address that one thing they started. Yeah they'll say " oh she's not dead" but they probably aren't going to do anything about it.