It's only fair that I acknowledge many sources...
FLOWERS FOR ALGERNON (which was made into the movie CHARLEY) was an obviously strong influence. Daniel Keyes fable about a mentally handicapped man who becomes a genuis and tragically, falls again, was one of the high points of sixties' sf. The whole Mindmistress/Lorelei duality was strongly influenced by that. Besides...I always liked the constrasting secret identity, corny as it might be. Mighty Superman, meek and mild Clark Kent. Hyper-fast Flash and slow Barry Allen. Uninhibited Spider-Man and science geek Peter Parker. Vive la difference, or something.
Oddly enough, BRAIN WAVE is one of the few Poul Anderson novels I have not read, but I know the basic idea/premise behind the book, and the idea is a very interesting one which has some implications for MM.
The Doc Savage series by Kenneth Robeson/Lester Dent....Doc could do anything it was humanly possible to do. Superman was a kind of take-off of Doc (mixed with Wylie's GLADIATOR) exagerrating Doc's strength and senses to superhuman levels. Superman had a super-memory, a super-intelligence (rarely used...) and super-hypnotism, at least in the later stories, but I think they died in CRISIS. MM is sort of a take-off in the other direction than Superman went---Doc knew a hundred languages, was expert in many fields, and had memorized the maps of many cities. MM is sort of if Superman had just had the mental powers---or if Siegel had exagerrated Doc's mental powers instead of his physical ones.
THE FANTASTIC FOUR by Stan Lee and Jack Kirby. The real hero of the book, and oddly enough my favorite character, despite his woodeness, was Reed Richards. Reed had Plastic Man's stretchiness, but his main usefulness to the team was that he was an unbelievable smart uber-scientist...creating incredible aircraft, spacecraft, portals to Negative Zones, intelligent robots, artificial life. Nine-tenths of the time he's the one who saved the day, and it almost always was because of his intellect, not his powers. Doctor Doom, his opposite number, didn't even have powers, and always fought them to a standstill. Reed was as unbelievably proficient in multiple fields as Lex Luthor, Fu Manchu and---there's that name again!---Doc Savage, and did everything from advanced chemistry to cosmology to nanotechnology. No real scientist would be as proficient in as many fields as Reed was. (Unless, of course, his or her mind was stimulated to ultra-intelligent levels by a process that...)
THE LEGION OF SUPER-HEROES: Brainiac Five proved that ultra-intelligence could be a honest-to-gosh super-power. However, he was always inventing machines that backfired on the Legion. He still jumps when someone says the name, "Computo".
ODD JOHN by Olaf Stapledon....the first novel I know of a "homo superior" and still one of the best at imagining what the next stage in evolution would be like, and how freakish a superhuman intellect would seem to us....and us to him.
All of these were influences, roughly in descending order, FLOWERS being number two, BRAIN WAVE number three, Doc number four, etc. However, the number one inspiration for Mindmistress is...
The Greek goddess of wisdom was always my favorite of the Olympian pantheon, and I think Homer's too. Many comic book heroes had their genesis in mythology---some closely, like Thor or Wonder Woman, some modeled after, like Superman/Hercules and Flash/Mercury. Mindmistress was more like the latter...modelled after Athena, but not directly tied to mythology. The idea was conceived in the mid-seventies, in trying to think of a superheroic equivelent of Athena. Then the rest fell into place.
So now you know.