Hi DawnYou might suggest to your friend that her doctor or a dermatologist check her for Rosacea. My sister, who's been on PremPro for a number of years, has this problem. I think it's a skin disorder that's hormonally aggravated, if not caused, and my sister's cheeks and nose are always more or less red. It is treatable, though.
The other disorder that sometimes shows up with a butterfly effect of redness or rash across the face is lupus, which is an auto-immune disorder. There is no one, specific test for it, though, and usually there are various other symptoms like stiff joints, etc. Depending on your friend's health and any other symptoms, it might be worth it to her to at least ask her doctor about the possibility.
Hope this helps a little,