Car batteries and alternators go on the fritz all the time, flu symptoms start out of the blue, the neighbors kids begged you to help the find their lost dog, while not advocating lying as a way of life , these any many more are reasons that people can't make it to things they 'have' to attend.
Given all the negatives against making the outing , perhaps missing this one is not a bad idea.
The biggest flag is that you state you are scared you may 'give in' , like you are fighting a battle against some stronger force. It sounds more like the AV has you incorrectly convinced It can be stronger than You. It's an illusion , but unless you are comfortable in knowing that your inner strength can beat the AV every time, it would be wise to not put yourself in situation where the illusion holds so much sway.
Sit tonight out, call your friend in the am ( but maybe not too early and speak softly, sounds like she may feel like shtt), stay home so you can be more sure you won't.
My two cents