I agree with Prudie that the pregnant mother should not quit her job, but I think she should speak with a supervisor or HR director and explain that her co-workers habits are making it very difficult to remain productive, so much so that she even considered quitting. This is the type of disagreement between co-workers that HR is intended to handle. Regarding the food, HR may already have a policy that forbids employees from eating food at their desks. If not, they may realize that employees shouldn't be eating more than a small snack at their desks. If the message comes from HR rather than the expecting mother, it would help mitigate any ill will between colleagues.

On a side note: Honestly, it's kind of disgusting that people are eating popcorn while using their computer. Mmmm...movie theater buttered keyboard.