I would say the same. Also, bloodwork should be able to confirm. I have heard of cases where women can convince themselves they are pregnant, and not only have symptoms but actually start to show. They aren't crazy at all, its just the mind playing tricks on the body. Sorry, thats the best I can do. I am not sure if you are aware, but this forum does not contain any Dr.'s. Your question might get a better response on the Ask an Expert Forum. Best of luck to you and your friend.
I'm no medical expert but the only sure way to know if your friend's pregnant is if she got a medical exam to confirm her condition which should include an ultrasound. If there's a baby in there, depending on how far along she is, they'll see it and confirm & date the pregnancy.
It's extremely difficult to judge pregnancy just from looking at the belly. I don't know very much pituitary tumors so I don't know the effect of such a tumor would have on the body.