Yes, speaking the truth can be harmful, and any harmful speech is Lashon Hara.
To ensure right speech, we must do two things. First of all, we must ask of each sentence, word, and phrase, "Is it true? Is it kind? Is it necessary?" Only speak if it is.
Second, we must consider how the information will be used, and how it might be misused. Even true statements should not be shared with people who will use those statements in harmful ways.
Of course, if those people have power and authority (including legitimate authority such as parents of children who live at home), this can be very challenging. In your example, it may be difficult to realize that one's own parents might speak in harmful ways. But if you believe it to be true then you must act rightly and refuse to tell them.
I am assuming that you are over 13. If you are, then you are an adult woman by Jewish standards, even if not by American standards. Live in a Godly way and do not help anyone - not even your parents - speak in harmful ways.