Naomi was angry because no matter what she said to Harumi, she never listened or obeyed. Whether it was to talk to the head nurse and allow her to speak with her mother or anything else in general. That's why her true colors showed, making her curse and insult Harumi multiple times.
When Ashley heard what her mother-in-law said, she could no longer keep calm, as this was the absolute last straw, so she walked over to where they were to protect Harumi.
