My budgiess have laid 2 eggs, 1 is fertile and the other isnt. unfortunatley the female hasnt sat on them why?

My budgies are about 3 years ld, one female and the other male. they have a nesting box but i had not put anything in there. it has been about 3 weeks now since she laid the eggs, unfortunatley i was on holiday and mum noticed. the female has not paid any attention to the eggs at all and has not sat on them either. one egg is fertile and the other isnt. My mother placed some twigs and some cotton wool into the breeding box and although she did not touch the eggs with her hands she did move them about using the twigs. will this be the reason she has not sat on them?? when should i remove the eggs considering she is not paying any attention to them?? my husband says it looks like the female is carry some eggs as she looks fatter than normal. how often do tey lay eggs and if i move the 2 there will she lay some more??