Supergirl's Adventure Comics
.....Supergirl had her own series in Adventure Comics, starting with Adventure Comics #381 (June, 1969), where Supergirl faced off against "The Supergirl Gang" by Cary Bates, Win Mortimer and Jack Abel (with a cover by Neal Adams). Superman's appearance was a small one, as this was more of a team-up of Supergirl and Batgirl, bringing down a school of female thieves.
Phantom Zone villains like Jax-Ur and General Zod.
This continued on until Supergirl's run in Adventure Comics ended in Adventure Comics #424 (October, 1972), but Supergirl did work with the Justice League of America, including Superman, Flash, Green Arrow, Black Canary, Atom, Hawkman and more in Adventure Comics #423 (September, 1972) in "Treachery" by E. Nelson Bridwell, Steve Skeates, Mike Sekowsky and Bob Oksner under a cover by Bob Oksner.
Supergirl On Her Own
Supergirl also had team-ups with Zatanna, the mistress of magic, and Prez, the teen-age President, during this run (both of whom will likely get more coverage in a later column...).
Supergirl In Superman Family
Later issues of Superman Family had Supergirl facing Superman foes like Lex Luthor, Blackrock and the Master Jailer, as well as future Suicide Squad member, the Enchantress, before Superman Family ended with Superman Family #222 (September, 1982) as Supergirl slowly took over the title.
The Daring New Adventures Of Supergirl
Reactron, and Blackstarr...even facing off against new Superman foe, Ambush Bug!
It's no Crisis!