What myril said.
Mother is god in the eyes of a child, and no matter how crappy parents you have you still want to please them.
Nightreader, on the contrary to your OP, Regina didn’t want to kill her mom. Or well she wanted to, but she couldn’t herself. Otherwise she would have done that instead of banished Cora to Wonderland.
And as far as she knew, Cora killed Daniel, and when we saw her trying on her wedding dress she was obviously still effected by the shock. And when Snow told her she had told Cora about Daniel, you could see how Regina just snapped. She was already very emotionally effected and Snow’s confession just made it worse, and in her mind Snow was the one to blame.
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