Take a deep breath
Here is a link on SET
https://bpdfamily.com/message_board/index.php?topic=143695.0Good to get a refresher on SET better communication can only help when meeting with your sister.
You might also think about what your boundaries will be. You've already set a couple of boundaries by having this meeting in a public setting and keeping it short. If she starts throwing out those zingers do you have boundaries around that?
I think having a plan before hand can help if things become emotional, it's hard to think on your feet when emotions are high. I think preparation can help. I tend to come from a 3 strikes and you're out frame of mind... .
Zinger
Use SET to tell her that was hurtful
Zinger
Tell her your boundary (SET - boundary)
Zinger
Enforce your boundary
Hopefully all will go well and you have a nice lunch together but if it doesn't you can always leave... .this isn't mean, this isn't rude, this is taking care of you.
Good luck, I hope you have a nice visit with your sister.
Panda39