Hi. Welcome to Just Answer. My name is***** Thank you for your question. I'm glad that the kittens found good new homes. As far as with Lucy, are you curious as to if she may be pregnant again? Was she out / around possible males that were intact?
Ok. There is the chance she could be pregnant again. Females can come into heat in the first couple weeks after giving birth (not the most common but possible). There are lots of cats that if around intact males that will become pregnant again before the current litter is weaned. Here is a good link on this from just one humane society.
The nipples could be swollen and the mammary glands more enlarged if she's still producing milk and getting that tissue to dry up. Is she still eating and drinking well?
That is good that she's eating and drinking fine. I would hope she's also urinating normally and not having any weakness. I would also hope she's breathing normally and able to get around fine too. The vocalizing she is doing could definitely be due to the kittens now being gone. As to her stomach being enlarged, could it be that she's eating more as the kittens are taking more of the food available? When I have enlarged abdomens in cats some thoughts are - eating large meals, pregnancy, fluid in the abdomen, masses, and their getting abdominal fat.
That is good that she's pretty much normal otherwise! I would feel that is a good plan to follow. I'm hoping for the best for her!