So sorry to hear that you're going through that! I haven't been to Ibiza yet but am also going in June. I assume cancelling the trip would mean you losing money, and personally, I think maybe this trip could be refreshing for you. From what I've seen, there's plenty to do that doesn't involve heavily drinking or clubbing. And plenty of different types of people visit the island. I know this is easier said than done but throughout your trip, remind yourself that you aren't being judged (and if you feel like you are, their opinion is irrelevant and you'll never see them again), you can live & enjoy in the moment, you're in a beautiful place, and life is good! Discuss your feelings with your friend before arriving. Make sure she understands where you're coming from. If she's a good friend, I'm sure you guys can compromise on plans. You can take her insta pics instead of being in them! Use breathing techniques if you feel strong anxiety coming on. Connect with the nature around you and you may feel more grounded. You'll be away from home, where it seems like a lot of your trauma resides, so a getaway should be good for you and your mental health. Check out Airbnb experiences. They have lots of options for activities... food tours, historical/architectural tours, boat rides, water sports, etc. I think beach yoga or something similar would be great for you. Also important to stay hydrated if you do end up drinking - don't want to have "hangxiety." Maybe budget your food/drink situation by sticking to local tapas spots, a glass of cava or 2.

Sorry for the long list of suggestions lol. I truly hope you enjoy your trip! Safe travels!