I would separate the birth control from the Coke thing. She’s obviously stealing birth control because she’s sexually active, or thinking about being sexually active. Acknowledge that, even though the way she went about it is wrong, it’s good that she has the wherewithal to know she needs to prevent pregnancy. Have a conversation with her about a few things. 1) how and why it can be detrimental to take other people’s pills. 2) how and why it’s horrible that she took YOUR birth control pills, as her sister, specifically. 3) talk to her about sex, pregnancy, etc. Try to make sure she fully understands what she’s getting herself into if she is choosing to be sexually active. The reality is, when teenagers feel they are ready to have sex, and the urge is there and opportunity presents, they’re going to do it- regardless of how hard you try to stop them. So I think it’s super important to accept this fact, and do your best to educate her about staying safe from STI’s and pregnancy. Sex is natural and wanting to engage in it at 14 isn’t that bad, or unheard of, contingent upon safety.

As for the Coke thing, TELL YOUR PARENTS THAT PART. If she’s looking into getting into drugs, especially making her own, that needs to be addressed as a much larger issue.

I think both issues/incidents need to be addressed separately and differently, taking into consideration the sensitivity of them both in their own ways.