StepMom advice; Found out my 12 yr old stepdaughter is in possession of Vape e-juice.

So my stepdaughter has been having a few issues. Earlier this year we found out she had sent nudes of herself to an anonymous person over the internet, and was then blackmailed for more. We involved the police and my SD had her phone revoked for months afterwards. She’s frustratingly always bringing my 9 yr old bio daughter into inappropriate conversations surrounding drugs, sex, sneaking out, etc.I always told my bio daughter that honesty goes a long way for me, and while I don’t condone tattle tales, I have an open door policy. If she tells me something, it’s up to me how I intend to deal with it. I can ignore it, or do something about it.This evening my bio daughter was cleaning her room and texted me “Mom, I need to talk to you privately NOW!!” and she told me that my SD was in possession of a Vape pen and liquid. I showed my SO the the text and he responded “Do you think my daughter is just fucking with your kid? And is just trying to get her riled up?” I agreed that very well could be the case, but we should take into consideration that there’s the possibility it’s true.When SD was in the shower, I check in with my daughter and she said “Mom, she showed me” so I said “Really? Where?” sure enough, my daughter went behind a picture on her nightstand and whipped out a 15ml bottle of 18mg Vape e-juice.What the hell do I do? I told my SO what was presented and he was obviously upset. He got on the phone with his ex-wife and she confirmed his daughter had stolen the juice.He’s upset at the fact that his daughter has been pushing the boundaries and his patience, and I’m sure it’s not helping the fact I’m sharing with him the things she’s telling my daughter.I get that she’s not my kid, and I have only the say he allows me with her. But when it involves my kid, I stand very strongly against the behavior.I feel this could hurt our relationship. I don’t want to ruin his relationship with his daughter, but I want to protect my own. I love his daughter as my own, and I’ve assisted in many confrontations about poor behavior with him and her, as he values my input.I could really use some Step Mom advice here. Should I pick and choose what’s relevant or important to tell my SO? Did I make the right decision here? Have I crossed a line?And how do I support my SO in this? Help me, please. via /r/Parenting http://bit.ly/2I18e7e