Never mind fertilising eggs – fleas can SURVIVE as long as they have blood to ingest. I’m afraid you’ll have to vacuum everywhere, especially in corners (the putting a cut up flea collar in the canister/bag is a good one – we always put the ends of collars we used in there. If the dog sat on anything, it will need laundering. Any soft furnishings ditto, if it can be laundered. You can get a commercial spray from a vet to use all over the house too.
And I hope you have warned your sister re what’s happened as she will have to be sure to treat her dog and ditto her house. He must have had quite a load to have caused such a problem in your home. It’s making me itch just thinking about it!