Does it annoy/bother you if you say hello to a person that you know and they say hello but do not make eye contact?

I think I've asked a similar question but I find it to be rude. It happened again today. I spoke to an old classmate, and they above happened. Yet she sits right next to me. But you can't even look at me and say "hello"? Does this mean I'm annoying? (Even though all I say was hey____) , does it mean said person/people do not actually like me, or are they maybe just insensitive and rude?