Don Markstein’s Toonopedia, Sun Girl’s powers were ill-defined, even though she had a three-issue run of her own title, and appearances in that publisher’s flagship title, Marvel Mystery Comics.
In this episode, from Marvel Mystery Comics #89 (1948), some odd-looking phantoms appear on the streets of New York, and Sun Girl is drafted to go after them. They have already cost one man his life, but plucky as she is, she goes into their dimension after them.
The Grand Comics Database lists Mike Sekowsky and Carl Burgos as artists. With this issue Marvel Mystery had just a couple of issues left to go before cancellation. The core group, Human Torch, Captain America and Sub-Mariner were still appearing in the title, but the comic book that had launched the publication company that later became Atlas Comics and then Marvel Comics, was gone before the 1950s began.