Hen hasn't layed for 2 weeks and fluffed up

You need to give us a better idea of what could be wrong to even make a good guess. You need to look her over carefully for any wounds or bumps, parasites (esp. around the vent and under the wings, also raised leg scales; some lice/mites only get on the birds at night.) Feel inside to see if you can feel an egg, or at least feel for one outside. You might consider talking to your vet about ding a fecal for worms if you have not wormed them with a wormer such as Valbazen or Safeguard. Is she eating / drinking? Are the others keeping her away from the food and water? And answer these questions:

https://www.backyardchickens.com/t/3569/have-an-emergency-disease-please-read-first

 

That sounds like she's egg bound, all fluffed up. Is her tail dropped?