As someone already beat me to the punch pointing out, Stevie does have several years of college in her background, and she worked in a dentist's office for an entire day!
She was a major drug addict who managed never to get arrested, and never photographed in an
entirely incriminating or scandalous manner. More than her being fortunate, which she was, it shows she had brains and survival instincts.
Stevie was able to keep the love and devotion of her father, mother, family and fans when many addicts wind up completely abandoned by those closest to them (Judy Garland, for one, who was no dope, but wore everyone out.)
Stevie, also, far and away, had the most success of any member of the band, though many have pointed out her talent wasn't as prodigious as Lindsey's. If any of the other members of Mac were more intelligent than Stevie, they weren't too smart about being left with (gold) dust in their faces, no member of Fleetwood Mac even came close to her career achievements on their own, compared to her.
Imo, imo, imo, I must stress, for any offended: Stevie is the clear choice for the most intelligent member of Fleetwood Mac, by far
(and to think, just a few days ago, I was completely slamming her in a thread on the Nicks Ledge board, because of what I think is a spiritual/ethical recklessness that makes me feel creepy, just in one certain song- 'Sorcerer'. I was wisely advised not to take 'it' so literally)-