Her final penciller there is Pete Riss. There seem to be a number of inkers—or finishers—some obscuring his style more than others. On this page from "Mary Marvel Fights the Likeness Peril" the woman in green, especially in the middle tier (note her arms), is the best example of Riss's pencils.
There are no Mary Marvel strips in 52, 56, and 59, as those issues' Marvel Family stories are full-length. The Mary story in 51, like the Marvel Family lead, seems to be out of inventory from a number of years earlier.
Mary Marvel in Marvel Family
Penciled by Pete Riss
|Jul/50||49||MM and the Adult Children|
|Aug/||50||MM Battles the Melody of Crime|
|Nov/||53||MM Battles the Evil Exterminator|
|Dec/||54||MM Battles the Predatory Plants|
|Jan/51||55||MM and the Miser of Resources|
|Mar/||57||MM Battles the Collector of Hate|
|Apr/||58||MM Fights the Likeness Peril|
|Jun/||60||MM and the Man Who Killed with Kindness|