A vaporizer is a excellent idea. When you smoke marijuana out of a bowl, bubbler, bong, etc. you burn the entire plants material along with somewhere around 300 chemicals. A vaporizer slowly heats up to the exact temperature that the chemical THC burns. This way you only smoke the THC out of the bud, and the plant material is left virtually untouched. This is the safest and healthiest way to smoke marijuana but detracts from the experience as there is little smell or smoke. Many make the sacrifice to avoid detection but many who use medicinally use them for the health benefits. Many find them more effective than even bongs as well. Very serious smokers will invest anywhere from 700- thousands of dollars on a good vaporizer and then never buy another piece in their lifetime. 500-700 dollars will get you a volcano, which many swear by. Be prepared to spend at least 150-200 dollars for an effective vap (an 150 dollar standard box vap will do the trick). Anything less might not work so hot.
The same is for brownies, cake, cookies, etc. The THC is baked away from the plant material in making cannabutter. There is still no ratio or recipe for potency but if you friend normally has mids I would recommend that she uses a half ounce for an entire batch. I'm an experienced smoker, did the same thing, ate 5 brownies and was so messed up. She should make them, eat one, wait 2 hours and see how she feels. If nothing, wait until the next day and try eating 2. Again wait two hours to see how she feels. That should do but she could try eating 3 or 4 if needed. If thats the case she could use an 0 and only have to eat one or two.