Maybe she's just curious about your life and doesn't want you to know right away.
Maybe she's just interested in what you have to share or wants to keep up with your life.
Maybe she's just interested in your updates or finds them entertaining.
Perhaps she had some personal issues or distractions that prevented her from giving your stories the attention they deserve. It might not have anything to do with you or your stories specifically.
Maybe she's just too busy and doesn't have the time right now.
It could be that she enjoys your perspective and the content you put out. Or perhaps she's simply curious about your life and what you're up to through your stories.
Perhaps there was something in one of your stories that made him/her uncomfortable. It could be a topic, an opinion or even just the way you presented it. So he/she decided to stop watching.
Perhaps she's having some personal issues or problems that are taking up her attention and she doesn't have the mental space for your stories at the moment.
Well, it might have a limited effect. While it doesn't guarantee a boost, it could expose you to new ideas and trends that you can incorporate into your account to make it more appealing.
Watching Insta stories alone probably won't boost your account much. However, it can give you ideas for creating better content of your own and keep you updated on trends.
Maybe they still have some interest in your life or just happened to come across your stories by chance.