Nanny McPhee's story is about how she uses her magic and wisdom to guide a troubled family. She has strange looks but a heart of gold, and helps the kids learn values and grow. It's a tale of love, discipline, and change.
Well, in the world of the 'Nanny McPhee' tales, she is a rather magical and powerful nanny. 'You are the end of the story' might be a statement about her being the solution to all the issues in the story. For example, she uses her unique methods to teach the children lessons and transform the family's situation. So, her presence signals the end of the story's main conflict as she is there to set things right.
There could also be themes related to the magical aspects of her pregnancy. Since Nanny McPhee is a magical being, her pregnancy might have some special or unexpected magical consequences. For example, the unborn child might have an influence on the magic around the household even before being born, or Nanny McPhee's powers might change in some way during her pregnancy.
One idea could be an OC who has a special talent for music. The OC could use music to soothe the unruly children in the story, much like Nanny McPhee uses her magic. For example, when the children are about to have a big fight, the OC plays a soft melody on a flute and they all calm down.
It might signify that Nanny McPhee is the ultimate resolution in the story. Just like how in a story there's a beginning, middle and end, she represents the end where all the loose ends are tied.
A believable OC should have flaws. Let's say your OC is overly confident in their abilities. This could lead to problems when they try to solve the children's issues. They might think they can handle everything easily but end up making things worse. Their growth throughout the fanfiction is also important. As they face challenges, they should learn from their mistakes and become a better person, just like the characters in the original Nanny McPhee story.
Another option is FanFiction.net. However, the quality can vary a lot. Some stories might be really well - written, while others not so much. When looking for Nanny McPhee pregnant fanfiction there, you might need to dig a bit deeper and read the summaries to find what you're interested in.
To develop Mare, you can focus on her internal struggles. For example, her feelings of guilt or her fear of losing those she loves. You can show how these emotions influence her actions and decisions in the fanfiction.
I don't know who the author of the 'Evangeline novel' is. There are so many novels out there, and without more context, it's difficult to determine the author.