Velma isn't the only girl sleuth whom some have interpreted as gay. Anybody remember Cherry Ames?
In the mid-20th century, readers could choose from three series about girl detectives: Nancy Drew, Trixie Belden, and last, Cherry Ames, created by Helen Wells. Wells and Julie Tatham, the Trixie Belden author, wrote 27 books in the Cherry Ames series altogether.
Cherry was, of course, utterly wholesome and cheerful and perky. She dated occasionally, but had no steady boyfriend. Most of the book jackets showed Cherry in her white uniform and often proclaimed on the back “It is every girl’s ambition at one time or another to wear the crisp uniform of a nurse.” (Indeed, the books always paid careful attention to the uniform, describing it and Cherry’s off-duty snappy outfits in great detail.)
Cherry didn't have Nancy Drew's staying power, and by the 1970s her books were out of print. The character had a rebirth in the 1990s, however, when Mabel Maney created a series of gay parodies of the girl-sleuth series books, bringing out their (almost certainly unintentional) lesbian subtext. In her first book, The Case of the Not-So-Nice Nurse, lesbian detectives “Cherry Aimless” and “Nancy Clue” discover more than just the solution to the mystery. And guess what? This and the follow-up book, The Case of the Good-For-Nothing-Girlfriend, include a lesbian character called, you guessed it ... Velma.
(The main source for this blog post is my own entry on Cherry Ames in the St. James Encyclopedia of Popular Culture, published 2000.)