Child's exposure to drug dealing

Hi mums
Please be gentle on me with this as I'm pretty upset and confused. I am certain that my sister in law is dealing drugs out of her home in front of my 10 year old niece. My brother in law who is already in jail for dealing was living with them selling drugs from their home and the house has been searched a number of times and he was arrested in front of her. Now a few things have added up that my sister in law is continuing 'the family business' - every time i see my niece she has a new iPhone or tablet or talks about holidays she is going to go on and has large anounts of cash on her, her mum seems to have more cash then what makes sense for her usual financial situation as a single mum. I have also noticed and had others say to me that she looks like she is taking drugs herself. Talking with my niece tonight she said her uncles 'friends' still come over a lot to see her mum and give her money and sometimes when her mum isn't home she takes the money and gives them what mum tells her to (I am aware she is too young to be at home by herself too let alone dangerous). We have a poor relationship as she is a very aggressive person and has threatened my safety a number of times. My husband is worried of doing anything as he doesn't want to upset his own mum about it. What do I do? I'm concerned if I confront my sister in law that my niece will be punished and we don't have a relationship where she would open up to me anyway. Please any suggestions would be great! I am worried for my niece but need to approach it as safely as possible for her.