OK! Just watch and observe her for signs she may be laying an egg! Being so young she could lay one on the cage floor, or also while swinging, or off the perch. If you see her on the cage floor setting, be right by the cage, and watch her movement there. When she lays an egg, she sets there, and if she is in good health, and the egg shell is hard, she can push it out. Plenty of calcium in her diet is necessary to make the shell hard. If she seems to be unable to push out the egg, gently pick her up, and look under her, to see if she does have an egg there. If so, that may signal she is egg bound. Then, you do nerd the vet asap! Hopefully, she will be able to push out the egg. When that happens you should see the egg roll out from under her.

With such a young hen, she still may not be fertile, so even though the pair is mating, her little reproductive organs are not fully deverloped as yet, so there would be no eggs forming inside of her. Then, that bump in her abdomen is a concern to me. P!ease keep us posted.