If I know a friend also sh, should I tell them that I used to do as well?

Last year in school, a friend told me to come closer and she has a question, she rolled up her sleeves, said don't tell anybody and asked me if she should wear long sleeves During PE, And I answered it is her choice and whichever way is comfortable to her she should do it. After a year, I started self harming as well, so should I also share with her about the same struggle? Or is this going to be a burden and trigger for her? She usually wears long sleeves so I do not know if they have been clean for a while or not, but recently I noticed some odd circular injuries on her fist, and I asked her is she Ok and she just replied yeah it is fine just minor silly Injuries, but the wound kinda look like a self inflicted burn scar???? Also, I saw her bandaged arm one day and she said it is fine too. She always get injured so I am pretty sure those are likely to be self inflicted injuries. I am really conflicted about if I should share with her or not since she might already forgot that she told me about her sh as well. Thank you so much for reading this thing!!!! Please also share your story and advice if you have similar experiences!