Why do some people say hi to just one specific person in the house or room? Is it to ignore the other person?

This has to do with my mother in law, most of the time she will just say goodnight son or bye son to my boyfriend when she knows I am there too. I dont know if she does this on purpose but makes me feel like am being ignored, but Idk because other times I say hi to her and she replies normally but I do know she may not like me because she has argued with her son about me when she was drunk...??