My female budgie laid eggs. Why are she and the male fighting?

Thanks for your question about your budgies. It isn’t typical for the pair to start fighting, but it wouldn’t be unheard of either. I didn’t see if this was their first clutch together, but sometimes that can make a difference. I would recommend ensuring that there is a great deal of space for them to get away from each other, and lots of resources available. Multiple food dishes, numerous hiding spaces, etc. Also, keeping any additional stress to a minimum would be important - things like new people coming over, loud sounds, etc.
I hope this gives you a place to start, and thanks for using Petco Pet Education Center, formerly Petcoach.