One should keep in mind that during her “Secret Weapon” years Supergirl operated under FAR more restraints than Superboy did. Until she was adopted by the Danvers, Kara had to maintain her civilian identity at all times, with only one Linda Lee robot to cover for her. In comparison, Superboy had the active participation of the Kents to provide alibis, plus a small army of Clark Kent and Superboy robots. More importantly, Superboy operated in the open, while Supergirl had to keep herself hidden from sight WHILE acting as a “Guardian Angel”. Thus, Kara had to be more innovative and inventive when using her powers. And for the most part she succeeded spectacularly.
Let’s review Supergirl’s major appearances with the Legion of Superheroes (relying on DarkMark’s invaluable Index at
http://darkmark6.tripod.com/sgirlind.htm ):
In Action Comics #267, Supergirl passes the Legion membership tests with flying colors, only to be disqualified because red kryptonite (temporarily) turned her into an adult. She has no problem gaining membership in Action Comics #276.
When fighting the Infinite Monster in Action Comics #285, Supergirl immediately recognizes that the Monster uses a force field similar to Brainiac 5’s, and quickly sends a message to the 30th Century for a miniaturizing ray. See:
https://www.supermanthroughtheages.com/tales3/greatest/Supergirl defeats both the Positive Man and Negative Man, and joins with Streaky’s descendant Whizzy to rescue the Legion from the Chameleon Man in Action Comics # 287.
In Superman #156, Supergirl exhibits her leadership skills by rallying the Superman Emergency Squad, the Legion, Superman robots and even the Atlanteans (Lori and Jerro’s people) to complete Superman’s unfinished projects before he dies. She later discovered that Superman’s malady was NOT caused by Virus X. See:
https://www.supermanthroughtheages.com/tales3/lastdays/Satan Girl nearly kills the female Legionnaires in Adventure Comics #313 until Supergirl and the Super-Pets stop her. Satan Girl’s realization that she can maintain her separate identity after 48 hours by siphoning her red kryptonite radiation into the Legionnaires is a stroke of (evil) genius.
In Adventure Comics #334, even while suffering from red kryptonite amnesia, Kara still recognized the need to conceal her identity and assisted the Legion as “Unknown Boy”. In appreciation, the Legion erected a statue to the Unknown Legionnaire, "The Greatest Super-Hero of All Time!"
Supergirl discovered that Amabassador Thora was behind “The Mutiny of the Super-Heroines” in Adventure Comics #368, and stopped her plot.
After learning that one Legionnaire must leave, Supergirl immediately cites her frequent absenteeism as grounds for resigning in Action Comics #387, thus demonstrating her concern for the Legion’s well-being. (She reconsiders when the Super-Pets beg her to remain, and Superboy leaves instead.)
By Superboy #204 (when we see Brainy’s infamous “Supergirl lovebot”), Karal was more convinced that she cannot continue being a part-time Legionnaire until she settles her life in the 20th Century. But the semi-retired Legionnaire answered the call and takes on Darkseid in Legion of Super-Heroes #294. She stays in the 30th Century from Legion of Super-Heroes #300-303 and Legion of Super-Heroes Annual #2 (the Legion anniversary, a battle with the Emerald Empress and the wedding of Princess Projectra and Karate Kid). But after fighting the Dark Circle in Tales of the Legion of Super-Heroes #314-315, a somewhat discouraged Supergirl bids farewell to the Legion and the 30th Century for what promised to be the last time.
Though her career with the Legion was spotty (there’s a couple more adventures that were mentioned in passing in other stories but never documented), Supergirl usually had a major contribution. But except for her fight with Darkseid, it was mainly her intellect rather than Supergirl’s physical powers that proved invaluable.
That was Kara Zor-El’s TRUE strength – her brain and her heart. We have yet to see whether the new Kara exhibits the same level of genius AND caring that typified her Pre-Crisis namesake.