Even if she doesn't know me personally why can't we just get to know each other?

In my previous post I shared about this girl whom I messaged on Instagram yesterday. We were in the same school in high school but she was probably a year or 2 my junior. We have similar sounding names and I remember the boys in my class used to tease me because of that whenever teachers used to call her name to give her some prize or medal in school. Anyways she is 20 or 21 now and I just turned 22 very recently and she says she can't remember she even talked with me in school. Then she was keeping my messages on seen and at last I asked her what did I say wrong and then she says she doesn't remember me personally so she isn't comfortable chatting with me. Why would she say that? Why can't we at least get to know each other? Its just an online chat. Its not like I am asking her for a date or something. If we don't know each other, then we can just chat normally and get to know each other. Like on this site, we chat with complete strangers and on dating apps too we match with complete strangers so whats the problem with her? Is it because I am not attractive enough and if I was more attractive she wouldn't have had any problems?