You can also use props or references that might be relevant to her. If you're telling a story about a book and you know she likes reading, mention a character from the book that she might be interested in. 'There was this character in the book, I think you'd like her because she's really into the same kind of adventures as you seem to be.' This shows that you are thinking about her while sharing the story and encourages her to be more involved.
First, you can try to have a private conversation with her. Politely explain that her watching makes you feel a bit uncomfortable. For example, you could say 'I feel a bit self - conscious when you watch me while I'm talking, could you give me some privacy?'
Find something else that you're actually interested in. When you have a more appealing alternative, it'll be easier to turn off the current story. You could think about your hobbies or things you enjoy doing, and look for content related to that instead.
It could be that her boyfriend is a great storyteller. His way of telling the story might be so captivating that she gets really into it. Also, if the story is about something they both experienced or something that is important to their relationship, she would naturally be crazy about it.
Look at his body language. If he seems more interested in other men's appearances or has a lot of male friends with whom he is overly affectionate, it could be a sign. But this is not definitive.
My boyfriend is a coffee lover. He has a special way of making coffee. He grinds the beans just right and uses a French press. The coffee he makes is always rich and full - bodied.
My boyfriend's cooking is amazing. He once made a delicious pasta dish from scratch. He carefully selected the fresh tomatoes and basil from the market, and then slowly cooked the sauce to perfection. The aroma filled the whole kitchen.
Sharing cooking stories can be really fun. My boyfriend's specialty is baking. He bakes the most amazing chocolate chip cookies. He has his own secret recipe that includes a special type of chocolate and a touch of cinnamon. Every time he bakes them, the whole house smells heavenly.
Coaching can be such an inspiring thing. If your boyfriend is a coach, I bet he has some great stories. My boyfriend coaches a little league baseball team. He once had a player who was really shy and lacked confidence. But through his coaching and encouragement, that player became one of the best on the team.
Just focus on her. Look her in the eyes and nod your head to show you're following. Don't interrupt her.
Maybe it's because you're waiting for it to get better. Sometimes a story starts off slow but then picks up and becomes really interesting.