Cannot Attend an Event Letter

How to casually tell a friend that you cannot attend their event without making such a big fuss over things.

Dear Ludivine,

Please tell Marnie I cannot attend her event. I'm a busy bee this weekend.
I really do feel bad for missing out on the party of the year.
But I really have to be up North for work. Oh darling, you know how it is.
Post your photos okay.

Much love,
Coco

Unable to Attend Event Letter

Dear Event Organizer,

Just wanted to say that your upcoming event looks fantastic! I wish I could make it though. I will be working that evening, but still I wish all of its attendees the best and hope you have a wonderful night.

Cheers,
Party Patty