Smoking weed at 14

My 14 year sold was caught with a weed pen she also went through a stage where she was suicidal, my mom and I recently also found some inappropriate pictures and videos of herself on her phone which we know she was sending to someone. My mom is a single mother of 4 I am the eldest. My 14 year sister does not like to talk any of my sisters or my mother we have tried therapy she refuses to talk about her feelings we have taken everything away such as phone computer which just seems to make everything worse. I keep telling myself that this is a phase and it will pass but things just keep getting worse.We are at the point where we are scared to leave her by herself because we don't know what she'll do. Does anybody have recommendation, advice anything helps.

Thanks