Finger tips numb and white, can't see my veins.?

A friend of mine has this problem where if she goes outside in the cold for too long, two of her fingers go numb and the blood rushes away from those particular fingers. Also, she is really pale and you still can't even see her veins. Whenever she goes to the doctor, nurses can never find her veins and they need to get a specialist usually. She's not anemic. She does get sick a lot, however.