I don't think you should be overly concerned. It could be that she's just exploring different people's stories and yours caught her eye. There's no real indication that there's anything negative going on just from her not following but watching your story. In fact, she might eventually decide to follow you if she continues to be interested in your stories over time.
Maybe she's just casually interested in your story content without wanting to fully follow you. It could be that she enjoys the specific things you post in your story but doesn't want to commit to following your whole profile.
It might be that she is shy about following you. She could be interested in you or what you post, but for some reason, she doesn't feel comfortable with the idea of following. So, she just watches the stories as a way to keep in touch without making it too obvious. For example, she might be worried about what others would think if she followed you.
You don't really need to overreact. Just keep posting your stories as you normally would. If you're interested in her, you could try to make your stories more engaging, but don't be pushy.
It could mean she's just casually interested in your content. Maybe she doesn't want to commit to following you but still enjoys seeing what you post from time to time.
Yes, it's normal. People often browse stories without following the account. They might be interested in the specific content of the stories at that moment.
There could be several reasons. Maybe they just want to keep an eye on your updates without having your posts constantly in their feed. It might also be that they haven't decided if they want a more involved interaction with your account yet.
It could mean that they still have some interest in your life but don't want to be too obvious by following you. Maybe they are just curious about what you're up to without fully committing to reconnecting.
No, you don't need to be worried. It's probably just their way of being nosy or still having a bit of interest in your life in a non - threatening way.