(Admin here. Posting this headcanon again because.....well, "reasons". I've deleted the first one, by the way. Sorry....but don't worry, nothing changed.)
For those people who wants to interact, my version of Ib is mute. I will describe everything she does in the third person so you will know what she is trying to say or do. Or I will make Garry and Mary go with her and act as her translators. Also, Ib have "defective" lungs which causes her to get tired very easily. That's why she doesn't play outside or with other kids often and would rather just stay at home reading, drawing, or painting.