Being ditched and it hurt so bad?

I had the same thing happen with a 'friend' start of this, she said she was coming to my new years party but then i saw photos of her on fb at a club on new years...Her lame excuse was "everything's been stressful with my grandmother's visit and all"...doesn't even make sense right? The thing is, if you want this friendship to continue you're gonna hafta talk to her about it...just casually slip into "So how was Sunday with so and so? Did you get up to much" If she doesn't bring up the fact that she left you out and that she's sorry (like actually sorry not some bullsh*t excuse like said above) then she isn't worth keeping...