Beth could grow more confident and assertive. Working alongside Rick, she witnesses his decision - making and leadership in tough situations. This might inspire her to be more proactive. For instance, she could start taking on more dangerous tasks like scouting for supplies or helping to fortify their camp. And as she does so, Rick could start to see her as an equal rather than just someone who needs protection.
One plot idea could be that Beth and Rick form an unlikely alliance to rescue a group of survivors trapped in a walker - infested building. They have to rely on each other's skills, with Rick's leadership and combat experience and Beth's medical knowledge coming in handy.
The plot could involve Daryl and Beth trying to find a safe place to have the baby. They might come across an abandoned hospital and decide to fortify it. Daryl would have to fight off walkers while Beth prepares for the birth.
A good fanfic about Beth and Shane would have strong character development. It should show how they grow and change in the harsh world of The Walking Dead. For instance, Shane might start to see Beth as more than just a young girl and respect her survival skills more as the story progresses.