I believe you can set the privacy setting on the groups to limit who sees. or you can set her level to limit what she can see on your page. I wouldn't let that limit your options if you are really interested. tell her it's to get information for school, or a friend or don't tell her a thing. really you don't owe her an explanation..you could just have an interest in mental health. life is too short to worry about what someone on facebook will think of what you post or what group you belong to.