So frustrated with my sister

Ok, so this is the second child she has accidentally got pregnant with... The first she was 17 and in high school and now she's 22. She is 25ish weeks pregnant now. Has finally seen the doctor... And I thought she finally got everything straighten out... Was on the phone with her tonight and her breathing was off... She was smoking... Seriously! This ticks me off so much!! Ugh!! She knows she shouldn't but she says that she was stressed and needed one... I just don't understand. I know there are worst things she could be doing, it just frustrates me so much....