There's not enough information to really know who Lucy specifically is. She could be just a regular reader of fanfiction who took the time to rate this piece as M. Maybe she's part of a fanfiction community where people rate works to help others know what to expect.
It could be inspired by her dreams. People often get creative ideas from their dreams. Lucy might have had some vivid and interesting dreams that she wants to expand on and turn into a novel. She could be exploring new worlds, characters, and storylines that came to her during sleep.
I'm not sure what type of Jereff and Lucy Doujinshi you're referring to. If you can provide more background information or context, I will try my best to answer your questions.
Other dragon slayers could be her potential allies. They might recognize her skills despite her being a princess. Also, magical creatures who are enemies of the dragons, like phoenixes or griffins, could side with her. And some wise old wizards or witches who see her potential might offer their help.
She might start to blush furiously. Given her character, she is a bit shy when it comes to romantic matters. And then she might start to stammer out a response, not really sure what to say at first. As she composes herself, she could tell Natsu that she has feelings for him too but in a very gentle and sincere way.
Erza could also be a main character. Given her strong and motherly side, she would probably take on the role of taking good care of baby Lucy. She might be strict about following a routine for baby Lucy's care. Happy, the flying cat, could be another important character. He could use his unique abilities to search for clues on how to turn Lucy back to normal.
[The Sword Comes can be downloaded for free, but there is no link to download the entire book.]
While waiting for the TV series, you can also click on the link below to read the classic original work of "Dafeng Nightwatchman"!
" Mortal Cultivation Legend " was a Xianxia cultivation novel that was published on Qidian Chinese website. The author was Wang Yu. If you want to download the e-book of Mortal Cultivation Legend, you can go to Qidian Chinese website to download it. It should be noted that Qidian Chinese Network required a registered member to download the e-book, and some chapters might require payment to read.
While waiting for the TV series, he could also click on the link below to read the classic original work of " The Legend of Mortal Cultivation "!