I think I feel my cats rib sticking out?!

Ok... It's 11:30pm... I'm cuddling with my kitty who just got spayed on Friday and I feel her underbelly and it feels like her rib is sticking out?! I'm freaked out right now and not sure what to do... How could this have happened?

Is it the bottom one? My biggest cat has a wide chest and I can feel his ribs when I pet his belly, and one of his ribs toward toward the bottom sort of feel like it's sticking out. But when you look up cat skeletons, the last rib is unattached and can feel a bit pokey when your cat is in some positions. 

https://facinatingamazinganimals.files.wordpress.com/2012/05/feline-anatomy-skeleton.jpg

I think it's the bottom one... And she doesn't seem to be in pain... It just freaks me out... It doesn't matter what position she's in right now... I can still feel it