Health Canada recently issued an advisory to doctors reminding them that the ONLY thing Diane-35 can be prescribed for is severe, scar-causing acne when oral antibiotics have been unsuccessful, and is NOT to be prescribed for birth control.
I don't think it can get much clearer than that. If you need to prove it to your friend, the Health Canada web site has the notice posted. Do a search for "health canada" and "diane-35". CBC news had a big thing about it in January.
Seems doctors were prescribing it because the manufacturer was promoting it as birth control, but Health Canada has never allowed this use and only recently realize how widespread it's use had become by women who were only using it for birth control, thus the advisory.
If you want to know the technical details of the increased health risk, the HC site will provide that info too. (Basically, the risk of blood clots increases 4 times.)