Kaido and Yamato's relationship are still "fine" imo
There is a reason:
1. Her attack is named Thunder Bagua, instead of copying Oden's moves
2. She fights with mace, just like Kaido who also fights with blunt weapon (club) instead of going swordsman or dual wielding swordsman like Oden.
3. Kaido still wants Yamato to show up in the festival and meet Big Mom, instead of locking her in dungeon.
4. There are no scar in Yamato's skin, showing she is not being bullied by her dad or his subordinates.