Hi there, sorry to hear about you're friend, but I think the doctor right. I don't think she pregnant, sounds like something else is going on. I have 6 kids and it doesn't sound like pregnancy to me. Hope your friend find out what's going on with her.
It maybe a delay in her cycle there isn't anything to worry about if she still hasn't had it by two weeks time tell her to go to the hospital
Is your friend underweight? A woman will stop getting her period if her weight is too low. Did she lose weight prior to the 40 days?
Those at home pregnancy tests are foolproof, if they say she's not pregnant then I would say there is a 99.9% chance that she's NOT pregnant.
Freefalling
What I mean to say is it not to early to see that she's pregnant if she may be from an ultrasound ??
You think though an ultrasound can figure out if she's pregnant??
Better She go for ultrasound, that will clarify your doubts and indicate your problem