Novel DONA BARBARA has elements that remind me of a tale involving pirates in the Caribbean, published in 1921 (wonder if Gallegos might have read it!) by then-popular writer of swashbuckling adventure novels, Jeffery Farnol. I think he was British. (May be unrelated fact that DONA BARBARA includes British character who calls himself "Mister Danger", one of the few who gets upper hand over the Dona).
Titled MARTIN CONISBY'S VENGEANCE, dedicated to author's "Dear aunts", it is sequel to title character's adventures begun in BLACK BARTLEMY'S TREASURE. Vendettas that wipe out most of two neighboring families are also featured in beginning of book DONA BARBARA.
The most striking resemblance between novels DB and MCV are the two bloodthirsty women characters who seek retaliation for same tramatic event in their youth. Could be just coincidence: ancient British warror Queen Bodiacia reportedly fought Romans after what their soldiers did to her daughters. In early 20th century, it might commonly be thought that the only reason a "weak female" ("by nature", femininely passive) would act like a forceful (violent) man is suffering "a fate worse than death".
Young "Barbarita" lives on river boat with what are called pirates; bloody Joanna is granddaughter of a Spanish govenor and British (got to look up passage to quote here).
Another parallel shared by two novels: for both "villanesses", there is a mirror image character; DONA BARBARA's daughter (rejected from birth by her mother, she is cared for as child by the village idiot, so grows up "innocent" and unspoiled roaming the wilds of nature. (In tv version, same young actress plays "Barbarita" and her becoming-a-woman daughter.
Captain Jo has rival in childhood sweetheart also named Joan, who had Lady & protective worshipful knight relationship with hero--until he discovers her father is his worst enemy. Shipwrecked hero at one point mistakes Jo for his Lady Joan. I suspect both "evil" women will find redemption by an ultimate sacrifice. Likeness may simply be example of common dicotomy of "good/bad" views of women; former mostly passive, latter willful.
Compare strong women in those early 20th century stories with 21st century heroines for young readers in TORRIE QUESTS books; the first is TORRIE AND THE PIRATE QUEEN. Young Captain Anna, however, is not a pirate--she's trying to remedy what her pirate grandad did. (See woman author's profile at www.annickpress.com Like J.K. Rowling, seems like her gender was disguised by using initials so maybe boys will try her adventure stories!)