Wah - I didn't get anything!

[Bijou]

Yes, she should have contributed, but maybe there was a valid reason she couldn't.  I would have shared with her, too. 

Exactly what reasoning would be behind that? If I had a "valid reason", say, why I couldn't contribute to a pot luck, I wouldn't go around moaning that I wasn't invited to partake of what everyone else had brought. This wasn't a charity affair.
I think it would be a bad idea for the OP's colleagues to start a lottery group - she'd not contribute, but demand her share of any winnings they got.

Hopefully people would be as kind to you as that employee was to this woman, and invite you to eat, anyway. 

Her valid reason could be anything...medical stuff, extra expenses, family problems...the kinds of things people may not talk about...Sure, she could just be a freeloader...neither of us will ever know, will we?  Frankly, I wouldn't worry about it.

She "could" be just a freeloader? She expects people to give her presents but not give them anything - I think that's the definition of a freeloader.

Sure, she could be barely scraping by financially and couldn't contribute (although hey, maybe some of the other people in the group weren't rich either, and did some scrimping to come up with their contribution). In that case, though, the dignified thing is to accept that you won't be part of the basket-recipients.

Honestly, it's completely entitlement-minded. It's just like whining about why do people with MONEY (or friends and family with the same) get nice presents at Christmastime, when poor people don't? Because that's the way it is.

I have no intention of making this an argument.