Hi,
This isn’t a good sign for the newly hatched chicks if the female started another clutch, and is also attacking the male. Some females will turn on the male, and sometimes the male turns on the female. You can try removing one bird during the day and then switch them at night. With cockatiels, usually one parent sits on the eggs during the day and the other at night. She might calm down after a couple of days of this. But if she lets the chicks die, the best thing to do is remove the nest box, discard the remaining eggs and separate the pair for a while. We recommend a 6 month rest. Are these birds at least 2 years old? Younger birds should not be breeding yet, and this could be the problem if they are younger than two. In that case, I would keep them apart until both birds are over 2 years old, then try them together again. You should always rest your pair for 6 months between every clutch so they don’t get run down.
Thank you for asking Lafeber,
Brenda