I'm not trying to be a SS and say "ZOMG everyone I know must come out and cheer for me!" I certainly don't think a marathon carries the same weight as a wedding in terms of hoping your friends will be there and being disappointed when they aren't. (On the other hand, a lot of New Yorkers, myself included when I am not running the race myself, come out and cheer even when they don't know anyone who's running that year, just because it's fun to encourage people in that way.)
I'm trying to thank the people who do. They are free to come, or not. But yes, I'm paying for dinner. That's why I'm annoyed. I'm buying dinner out of gratitude for the boost I get from the cheering. So...if she's not going to cheer, it seems presumptuous to me to come for the free meal.
And, I was paraphrasing myself earlier. The actual wording was, "if you cheer for me somewhere along the course, I'll buy you dinner at XXX restaurant." I suppose my mistake was in sending the Evite to all and sundry. Maybe I should have just emailed around asking, "is anyone going to be on the marathon course?" and invited only those who answered yes.
That being said, I'll try to think of this as she's happy for me and wants to get together.