Well, it could go in many ways. Maybe they would be really protective at first, sizing her up to make sure she's good enough for Stiles. They might test her loyalty or her ability to keep their secrets if they're a supernatural pack.
Stiles is the key character here. He's the one through whose perspective we usually experience the story. In the pack, Scott is a must - he's the werewolf who has a long - standing friendship with Stiles. Derek, with his alpha - like presence, also plays a major role. Additionally, characters like Allison, who has her own arc related to the supernatural world, could be part of the main cast as well. They all interact with Stiles in different ways when he meets the pack.
One interesting plotline could be Stiles initially being intimidated by the pack but then gradually forming deep friendships. For example, he might start off being scared of their supernatural powers but as he gets to know them better, he realizes they are just like him in many ways, with their own insecurities and desires.
In some fanfictions, the pack meeting Stiles' family could lead to a lot of chaos at first. The pack has their own supernatural quirks, and Stiles' family might be shocked or confused. For example, they could mistake some of the pack's abilities for magic tricks at first. But eventually, they might come to accept the pack and see them as an extension of Stiles' life, leading to a big family - like bond.
Often, the first encounter is filled with curiosity. The pack wants to know what makes Stiles so smitten. They'll observe her every move. If it's a werewolf pack, they might even catch her scent to see if there's anything unusual about her.
Perhaps he feels that the other pack can offer him more opportunities for growth. In some fanfictions, the new pack might have access to different kinds of magic or knowledge that Stiles is eager to learn. So, he joins them to expand his skills and understanding.
One way is for the pack members to stand up for Stiles more often. If someone outside the pack is giving him a hard time, they should be there to protect him. Also, they could share their secrets with him, which would show that they trust him. This trust is an important part of any relationship and would help Stiles realize that they don't actually hate him.
His father could be one of the supporters. His father has always been there for Stiles, and he would understand if Stiles was standing up for what's right within the pack. Another possibility is Lydia. She's a smart and powerful character herself, and she might see the value in Stiles' actions and support him.
There could be. However, the popularity of such fanfiction might vary. It really depends on how the author portrays the 'pack is possessive of stiles' concept. Some might write it in a way that's really engaging, while others might not do it so well. You may have to search through different tags and authors to find the really good ones.