A pregnancy in a cat is much like a pregnancy in a human being. The vet can tell if it is pregnant through a blood test. Two weeks is a lot longer in a cat pregnancy than in a human beings, so it is easier to tell if they are.
Your vet may be able to tell at 2 weeks by doing an abdominal ultrasound to look for fetuses. Watch for "pinking" of the cat's nipples and increased appetite.
a cat's gestation is only 9 weeks, so at 2 weeks they are a 1/4 way through. Your vet would have palpated her abdomen, and been able to feel small lumps. It may not be 100% accurate, but a very well educated indication.
No, the vet will not be able to tell at this point unless they conduct an expensive hormone test. They usually listen and feel for kittens, so it would have to be much later in the pregnancy before they will be able to even begin to detect the presence of kittens.
