There is another guy in her life but hasn't told me about him?

she talks to me about all her friends except for him, she likes to hide him, never mensioned him to me,, but me being sly through facebook, i knew there was something going on between her and him.., i know exactly who he is, but as i added her on facebook she accepted and hid this album from me to see,, why is that? we arnt dating or anything we are just friends,,, i know they are just friends to,, but she hasnt told me about him.