I think my friend does sh, were both minors and ik she has a lot going on with her parents how should i talk to her?

Throw away account cuz im worried my friend will see this. Me 14f and my friend 15f were talking today and when i noticed purple scar in long lines (atleast 3) and i tried to look at it amd she didnt want me too see. At first i thought she burned herself while cooking but she told me that a dog bit her but i knew it wasnt that cuz she had been bit before and it didnt look like that. I think she understood that i didnt believe her cuz she said she didnt wanna talk abt it or let me see it. Also this week she came in a pretty shirt but the jacket was ruining it so i told her she should take it off but she didnt want to cuz she had an allergic reaction on her arm(not the one i saw tdy) usually i would be fine with that reason but but both of us were getting mad at my other friend for always wearing jackets cuz of her allergy scars. I asked to show the allergy scar and she did and it was pretty unoticable. I also asked if i could see her without the jacket but she absolutely refused which was weird cuz we were alone in the classroom and usually she would be happy and playful but i brushed it of cuz she had a headache and i thought i just annoyed her. Im really worried bcuz last time when the other friend refused to take of her jacket we bcuz of scars we both thought it was sh(it wasnt thankgod) and she was very seroius. Also a liitle thing is that she is constantly having fights with her parents and before that her parents would fight a lot and her mom would sh infront of her(dont wanna give too much details cuz its her life and not mine). I really dont wanna force her into a conversation but it seems its the only way because she is a very stubborn person and i always have to push her out of her comfort zone do something about a certain problem. I also am not sure what exactly to say to her, i searched it up but it was just tbe basics and nothing more. I dont even know how to ask her if it sh or not or that she wont lie to me cuz ik she could getaway with it. And after the conversation how should i keep up wuth her to make sure she doesmt keeo doing it. Therapy wont help cuz it didnt last time and since she is a minor it will probably be told to her parents which i assume are the main problem in her life.i really need all the adviceu can give. Also what dk i dk if it turns out not to be sh?? Please help me any advice is apeeciated any at all. And alsk i already told her we would talk abt it and she said she doenst want to but i told were still gonna. Other than that we havent talked abt it at all? Any advice please, once i can use since were bith minors??