Weird.
Even if drugs were legal, still weird.
And no, it's not a double standard; cause I know someone's gonna say "well, plenty of people drink with/around their parents."
Well, IV recreational drug use is a lot riskier than just downing a beer, some liquor, or some wine. It doesn't sound like she knows what she's doing, and I doubt that she knows exactly what your limit is. Just seems a little creepy that she's helping you do something that has such a fine line between "a good time" and "death."
I don't know, even as a user, I wouldn't want to have anything to do with my children's drug use. Just as I wouldn't want to have anything to do with their sex lives. (No, I don't have any children. Just hypothetical I suppose.)