From Adventure Comics #300, September 1962. "The Face Behind the Lead Mask" by Jerry Siegel, John Forte & Al Plastino.
The story opens with a typical Legion meeting. Look who's at the head of the table:
The boy Legionnaires' powers go berserk and break shit in the clubhouse. Saturn Girl is understandably annoyed (and prepares to take action) - but then her own powers get crazy. Yet Saturn Girl is the only one of the Legionnaires who CAN control her powers, apparently:
Thinking quickly, she decides it would be good to have Superboy around to help her solve the mystery. I love the big Python-esque lever she pulls (all homes should have one). Note how the boys just stand around with stupid looks on their faces watching Lightning Lad's mini-thunderbolts destroy more of the joint:
Then the plot happens and a mean guy with a lead mask named Urthlo shows up and says he's going to make them leave Earth so he can take over. Urthlo gives Superboy a taste of green kryptonite vision and all the Legionnaires run (fly) away. But Saturn Girl has a plan:
The plan involves bringing Mon-El, Superboy's boyfriend, out of the Phantom Zone. Superboy objects and Saturn Girl slaps him down:
So he does it, and as soon as Mon-El starts having vapors, Superboy panics. But Saturn Girl is all business. (I need to start saying "Nonsense!" to people when they whine to me.)
Then he's OK. Mon-El beats up Urthlo, who turns out to be a robot that teenage Lex Luthor sent to bully the Legion. (Thank you, Jerry Siegel.) (I think it was just jealousy over Mon-El, but that's just me.)
Saturn Girl reveals that she, her own self, developed a (temporary) cure for Mon-El! Telepathically! At a distance! While Mon-El was in the Phantom Zone! She was probably riding a bicycle backwards, too:
Then it's all better and Superboy leaves. Cosmic Boy is such a suck-up:
No, you dick, if not for Saturn Girl's quick thinking and being completely in charge and INVENTING A SERUM TO CURE MON-EL, you all would have been toast.
Word to your Imra.