You shouldn't let the birds have babies unless you have knowledge of what to do when birds begin to reach weaning age. Birds will continue to lay eggs even with a clutch of chicks in the nest, this is just what they do, especially the more prolific species like lovebirds.
I was in this situation when my cockatiels were raising their clutch. The hen continued to lay eggs and so I just threw them away until the babies she had were big enough to leave the nest and then took out the nestbox. She stopped laying shortly after I took it out. My suggestion would be to put babies back into nestbox so the parents can keep feeding them and then throw any new eggs away. If she's protective and continues to lay you could also take the egg, shake it around quickly to scramble the yolk inside and so it will not hatch that way.