How would you translate this? I understand that she couldn’t get angry, but why 怒るに？
The context:
ご飯が残らないのはおいしい証拠。
うちは共働きで、帰りが遅いのもしょっちゅうです。私は朝、夜ご飯の準備をしていきます。帰るのが遅くなると、ご飯が残っていない！その時の夫の一言です。怒るに怒れない。
No rice left over is a proof that it was delicious.
We both work, and I often come home late. I prepare the evening meal in the morning. When I come home late, there’s no rice left! This is what my husband said at that time. I couldn’t get angry.