<human>: Today I saw my sister's arm and they had a row of short cuts that looked like typical self-harm injuries. I asked her what happened and she acted surprised and said it must have been the way she was sitting. An hour later I looked again and they were still there. She's had this behaviour before - the first time I found cuts on her arms was a few months ago. My dad said that my sister scratched her arms with her nails until they bled after our mom was screaming at her. This time I suspect she did it after our mom had a huge fit and threatened to divorce our dad. 

I don't know what to do :( I'm very sad that she is doing this to herself, she's always seems like such a happy person. I just hope it isn't a regular thing and are only isolated instances. Both times our mom's behaviour/family conflict was (I'm guessing) what triggered my sister to hurt herself. Should I say something to her? I asked her about the first incident and she got very defensive and said she didn't want to talk about it. I'm afraid asking her again will anger her and drive her to cutting herself or hiding it even further. I always tell her that I care about her, but I wonder if that is enough. I honestly don't know if I should do/say anything else. Does anybody have any advice?

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: Found self-injury marks on my sister for the second time. Both times came soon after a bad episode of family conflict. Don't know what to do to help her.