They are probably ashamed of her eyes since it is such a unique color. She might be labeled a freak, witch, monster, et. Plus they don't want her to stand out
I assumed they indicated something special (though I'm not sure if Iris knows, her family - or her aunt, at least, does). Either they're just unique and so she'll be too attractive, or they actually mean she has some ability or bloodline connection that someone will take notice of, that will take away the advantage her uncle's family currently have over her.
(But it's all just speculation when there are only three chapters!)
i dont think they tried to hide her eyes because of that, her eyes probably showed that she is special or has some kinda power idk
Whats the story with the eyes?