My sister is 26 and still seems to constantly pick her nose?

She's done this as long as I can remember. It's literally every minute and it pisses me off because I feel she should've learned to use a tissue by now. I even try to make a point of looking at her every time and she still does it. Furthermore, she wipes boogers on the sides and fronts of seats of the car, on her pants, under tables, etc. I called her out on it once and she told me she's just scratching it or some other excuse. It's not only socially unacceptable at that age but very unsanitary. She doesn't have any mental problems except for a mild form of ADHD, is that relative? Is there anything I can do? I'm 19.