AITA for making fun of my sister's underaged drunkenness?

This is a throwaway. And I'll be as quick as possible. Please don't message me and ask unnecessary things.<br><br>My sister is 17. My mom and I went to her party last night and she was pretty drunk. It was annoying but mom seemed to take it in stride.<br><br>Now, a little background, mom is really bad at controlling her drinking. She started when she was my age, 13, and by 15 was drinking daily. That led to her being a heavy drug user and she eventually dropped out of school and just moved in with me.<br><br>Last night, after my sister went to sleep, I said to mom "You were 13 when you started drinking, that's why she can't be responsible at 17". To which mom responded "Well you probably shouldn't be saying this, you're not responsible yourself". <br><br>So, yeah. AITA?<br><br>ETA: My dad does not pay child support, has no legal obligation to, but does provide child support money which mom spends on herself and keeps for herself. I'm currently in therapy for my mom related trauma. And to be honest I am pretty drunk right now. Sorry for any typos.