I hope that you will go to the party since it is for a dear friend. Remember that others there might be feeling the same anxiety and you can be of some comfort to them by your presence.

You have gotten yourself through challenging times before. Have you ever thought afterwards that it wasn't so bad after all?

If I were in your shoes I would do some visualization and imagine myself going and having a good and relaxing time.

And please, start doing some deep breathing.