Hi,
She is probably coming out to eat & drink or he is feeding her. You can’t watch her all the time, so most likely she comes out when you aren’t around. Usually one parent sits during the day and the other at night. Possibly this pair isn’t bonded as a pair. If this is the case, they probably didn’t mate, so the eggs won’t be fertile. If both birds are over 2 years old, then just give them privacy and see what they do. First time parents make a lot of mistakes. If they are under 2, they should be breeding and this is the main reason they aren’t doing well. In that case, I would remove the nest box, and separate the pair until they are old enough.
Thank you for asking Lafeber,
Brenda