The internal egg making factory is pretty complicated. There are a lot of things that have to work right for a hen to make a perfect egg. It's not unheard of an old established egg layer to have an oops. When a pullet is just starting to lay it can take a while for her to get all the kinks out of that system. To me it is surprising how many actually get it right from the start.
There are certain triggers that tell a hen when to release a yolk to start that egg making journey. If she accidentally releases two at the same time you usually get a double yolked egg. If two yolks are released the same day but spaced out she can lay two eggs in one day. Often the second egg is soft or thin shelled, she only makes a certain amount of shell material and may run out for the second egg.
To me it sounds like your pullet hasn't gotten the triggers straightened out about releasing yolks. Sometimes a pullet or hen is defective and keeps doing that but usually within a week or two they straighten out and start laying one a day. I really don't know a lot you can do about that except give her time.
Good luck!
