Mary Marvel gets a solo story in Shazam! 14 (July/Aug 74).
Maggin and Oskner open the issue with a Captain Marvel story centring on Sunny Sparkle.
Sunny's "power" to get people to give him things is fairly well known by the time of this story, enough that a hood works with a criminal scientist to lure the boy in to be tested, and the essence of this ability duplicated.
The hood then sprays himself with the essence, and winds up with the same ability. He no longer needs to steal, as everyone keeps giving him things. Captain Marvel is immune to the effect, but struggles to find a way to force the man to stop. Finally he dresses up as an artist, and then refuses to give the man his painting. This makes the guy doubt the effect of the spray. He keeps spraying himself with it, but of course nothing changes, and Marvel still will not give him the painting. In disgust, he breaks the bottle throwing it away.
Yeah, not a great story. But it's a Sunny Sparkle story, what do you expect?
I also have problems with the Bridwell and Oskner Mary Marvel story in the issue, but it's the same problem I usually have with her stories. Mary Batson is invited to join the Mary Marvel fan club, who have recently constructed a new clubhouse in which to meet. It's surprising they were able to build it, as the girls must all be close to blind.
How can you tell their vision is severely impaired? Ghosts show up to haunt the first meeting. Mary changes into Mary Marvel, and none of the girls can tell its the same person, even though the only thing that changes is her dress! At least give her a pair of glasses or something!
The ghosts sure seem ghost like, and terrify the girls. Mary Marvel doesn't believe they are real, and eventually figures out that these are ghost bullets being fired by an old foe, Ghost Gordon, who had faced Captain Marvel back in 1950.