After Gokuu's death, Chichi changed a lot. She raised Goten in a far more relaxed way, not stressing Goten's education anywhere near as much as she had done for Gohan. She seemed to want Goten to grow up to be like his father, teaching him to fight and to enjoy fighting. I guess Goten's appearence and personality must have really reminded her of Gokuu, and she decided to raise him as Gokuu would have. She even dressed him in the same fighting gi. Perhaps she thought of him as some kind of replacement.

The one thing that seems to worry her is Goten's ability to tranform into a Super Saiyajin. Perhaps it reminded her too much of Gokuu (I'm not sure if they'll leave the translation in in the dub, but when Goten goes SSJ in front of her she stutters "Go...k...  ...  Wah! Goten's turned into a punk!!"), or maybe it was just that she hated Super Saiyajin as Gohan said.

At the Tenkai-ichi Budokai, Chichi supports Goten to the end, while Gohan had been worried if she'd even have let him enter. It just goes to show how much she changed in seven years.