Hi Khadijah,
You should take the bird to an Avian Vet as soon as possible. Birds need to be 100% healthy for breeding. And the male needs to be at least 2 years old, too. If she got sick after you put the male with her, he may have an illness that is not affecting him but has made her sick. Chlamydiosis is very common in cockatiels and some can carry it without getting sick from it. If this is what the problem is, the female will die without immediate treatment. It’s also possible that she needs to lay an egg and it is stuck inside her. This is also fatal if she is not treated by a Vet.
Take care,
Brenda
