Hi,
Birds do not get pregnant because they lay eggs and all incubation takes place out of the body. Having a mate, and mating does not have to result in eggs. When a parrot such as a lovebird is going to lay eggs, they can do so with or without a mate. Each egg takes about 48 hours to form and then she lays the egg. She doesn’t carry formed eggs inside of her.
I’m not sure why you thought she was pregnant? If it was because they were mating, again, that doesn’t have to result in eggs. It can be a good sign, but a pair might mate off and on for weeks without any eggs even being laid. She won’t be triggered to lay eggs unless she feels she has enough food and a safe, private place to nest. If she has been acting like she wants to nest and is going in and out of the nest box, it just means she is hormonal and thinking about nesting, and may or may not lay eggs soon. If she has some type of physical swelling, such as a distended abdomen, then something is wrong with her and she needs to be seen by a Vet. Most of the time there is no outward physical sign of an impending egg.
Thank you for asking Lafeber,
Brenda