Are there methods you usually use to make yourself more comfortable in public? Like wearing clothes you find comfortable, or taking someone specific with you?

Maybe discuss the party with her - tell her where you would prefer to go. Some places might be more comfortable than others. Even if it becomes a stay-at-home tea party; those can be really fun if you go all out with them.

Otherwise, try to go in without expectations and enjoy the small things like the lighting in the room and its decor, or your friend's conversation, or the food and drink - take something pleasant from it no matter how small.

Happy Birthday

┈┈┈☆☆☆☆☆☆┈
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┈┗━━━━━━━━━━━┛┈ (I stole this cake from an ASCII art site... don't tell anyone)