Graduation Party

So my sister is graduating pretty soon and she'll be having a graduation party in a couple weeks. First off, I should add that we're step sisters, even though to me, she just is my sister. So anyways, her "mother" if you could call the woman that, hasn't talked to her since she was bout 10, and my sister wants to invite her to her party. I know it's her party and whatever but I told her honestly, if her "mother" comes, she'll be told to leave or get the fuck out, whichever one. Our brother(again my "step") hates the woman and has told her go to hell, but that's not gonna stop my sister from trying to invite her. I may end up coming out as a bitch about this, but HONESTLY I'm trying to help her! I know she wonders why her "mother" gave up on her, answer is simple; chose a dumb boyfriend over my sister and brother. So that's the answer right there. My sister even has that as a to do before I die thing on her senior shirt, I'm just saying she's better off not knowing! Plus what pisses me off is the fact that she calls my mom her mom, so if she still thinks of that as "mother", don't call my mom mom!
So there's venting from me today
Nice to get it off my chest!
~Jamie Elizabeth