I dont think this is a problem. Your boy has had a different kind of life, where he has been able to express his rabbitude from an early age. Your girl didn’t get to do that as a youngster, because she wasn’t with you.

My bun Bam was an adult when he came to me. I dont know what kind of life he had before I found him, but judging from his behavior, he had been living in a cage or similar. It took him a whole year to venture out from under the coffee table  which he had chosen as his home base.

I had Bam for 7 years, during which time he became more and more outgoing, social and unafraid. I dont think a process like that can be sped up in any significant way – if you provide the bun with a safe and enriching environment, nutritious food and necessary health care (my Bam had fur mites when I found him), the bun will respond in its own time, at a pace that the bun sets.

I think your girl is happy. She is obviously very lucky. She is not done developing. She might still very well decide one day to come out of her cage without your calling her. She could do that tomorrow or 2 years from now, you never really know with buns. When an animal has grown up caged 24/7 it learns that initiatives are futile. (This is called learned helplessness https://g.co/kgs/88JLKM). Now she is unlearning this.

Every bunny is different. They have their own personalities and, as Bam pointed out, some of that can be influenced by early experiences. If a bunny is naturally shy and all they have ever known was a tiny cage, it may take more time for them to feel comfortable with the idea that they can venture out of their “safe space”. Continue to encourage her, but also keep in mind that she is going to ultimately set the timeline.