I don't know what to say

My best friend is kind of a loner except she has really come out of her shell this year. One thing That is making me nervous is her suicidal thoughts/tendencies. She tells me that she had to lock up the knive drawer in her kitchen because she really wanted to hurt herself, she also told me that she wasn't aloud to go to her swim competition because she was going to cut herself(she felt like she wanted to die) but her mom caught her so she had to be at home with her family and not out alone. There have been countless times when just out of nowhere she'll get a panic attack. When she tells me these things that she does to herself/wants to do I don't really know what to say to her. Also, i think she's telling me more and more of her self harming "habits" because we have gotten a lot closer this year, but do you think she's trying to tell me something? I honestly just don't know what to say to her when she tells me she wants to kill herself.she has a near perfect family life from what I can see and she even tells me her family is awesome so I don't think anything is going on at home, she's also kind of violent she punches her cousins and hits them and pushes them down the stairs (for what I can tell that's kind of what her entire family does when they want to have fun, the kids not the adults) should I be worried or is she just trying to get attention? :help: I don't know what to do either way