Is it me?

My best friend who I've known and loved since first grade has recently started acting distant and cold towards me. We've been close for over a decade at this point, and she's always been a lot quieter and less emotional than me. But as of late, it seems like she doesn't want to talk to me at all. She's not being mean to me, but whenever I say literally anything, she just gives the vibe she wants to be left alone. When I tell her things she used to find funny, she just looks at me blankly, as if I just said the most childish thing in the world. She's so much smarter and more talented than I am, so I'm wondering if it's because she feels like I'm not on her level anymore, or if I'm just not fun to talk to now that we're older. Sometimes, she straight-up doesn't answer when I say something, even when she clearly heard me. Over text, she's super friendly and enthusiastic, but in person, she's aloof and always seeming tired. I don't know if it's something going on in her life or if it's me. I totally understand that when people have things going on in their lives, they can act coldly to those around them. I just want to know what I'm doing wrong. I want my best friend back. I can't afford to lose her.