I think she needs to see a different doctor, to be frank. Energy drinks are not even proven to be 100% safe for everyday use by the non-pregnant population. Not to be rude, but does she have any idea what some of those ingredients are derived from?
I think your best move, if you want to push the issue, is to do a little research for her. A quick google will tell you that taurine (a popular ingredient) boosts the effectiveness of caffeine. So the can may say 80mg, but...
Sorry, I'll get off my soapbox now. Please try to discourage her, but don't ruin a friendship over it.
Good luck, it sounds like you'll need it!