Great underpants.

I kid you not underwear.
Hear me out.
My niece was bullied most of her life. I took her out at about age 8 and bought her adorable new underpants. Lot and lots of them. All her own colourful and random picks. I then explained that all superheros have great underpants. Superman... .red ones worn on the outside, batman black with built protection, wonder woman high wasted. I could go on.
I explained that part of facing fearful anxiety provoking situations is knowing that on some level you are amazing and have your own super powers. Her's are that she speaks multiple languages, has lived on the open ocean most of her life, has killer whales for companions, is super smart and strong etc etc. Mine are the I am smart, resilient, loving, kind, capable, etc etc. So now when she is facing bullies she just has to think ahhh yes but you don't know that I have my amazing powerful super power panties on so in truth I can access my superpowers at any time even though my power panties are not visible. You can't hurt me because I am amazing and I have power panties on that protect me. It has helped her immensely.
Its always makes her and I laugh when we talk about all the occasions that she has resorted to new underwear to get her through. She is 20 now. We still buy panties together once a year. WE still both keep a supply of brand new colourful ones in a drawer and take a pair out to wear on super stressful occasions. It is silly but it seriously helps. I face staff meetings, final exams, dealing with difficult people in brand new super power panties and new socks (I love new socks). The last time I dealt with my ex i did this and the whole time he was ... .well being him... .I kept thinking yeah but I have the most awesome squishy new socks and pink and blue superpower panties on and you have no idea how powerful I really am. So hit me with your best shot and I will laugh on the inside and keep my superpowers hidden because you can't get to me.
I also agree with the surround yourself with an image of warm empowering light. Don't drink... .it lowers inhibitions and well you need your wits about you. I smile and act like he has no power over me. I know it hurts but its not worth letting them have the satisfaction of knowing they hurt you. We are strong and worthy of being treated well. Go in with that expectation and if she is cruel or rude just give her a quizzical look and say "wow how rude" and walk away. Then go laugh and visit with someone else. It will hurt like hell but it will build strength in you that you never knew you had. Also don't end up alone with her ever. Witnesses always just for safety sake. And remember you have your own superpowers and your underwear are evidence of that. She will never know how awesome your amazing cool powerful underwear are. They are yours and yours alone and she has no knowledge of them, or you, or your powerful resilient self.
Ok now go buy some underpants to wear for your special victorious occasion.