I don't really think any actress - past or present - really typified "girl next door" more than Joan Leslie (well maybe Dawn Wells/Mary Ann comes close). She was as cute as a button but seemed very unglamorous (and was apparently very sweet person and a lifelong devout Catholic in real life). I remember the film Hollywood Canteen, a for charity WWII propaganda piece of perfectionary (which was filled with WB stars, since the other studios wouldn't allow theirs to appear - even though all types were at the real Canteen) Ann Sheridan originally went on suspension rather than appear in the lead since she didn't believe it was realistic to show a regular G.I. falling in love and getting involved with a real movie star (and it was against the actual Canteen's roles). So Joan Leslie filled in, playing "Joan Leslie" (and I believe her real sister played her real sister, though her on-screen parents were actors) having a romance with Robert Hutton's "Slim". Ann Sheridan was right. It was unbelievable. The only movie actress I could see pulling it off was Joan Leslie.
She's also a great example of the Hollywood "Star" system at its best and worst, in manufacturing and discarding actors. By the time she was 20, Joan had been the leading lady of Gary Cooper (Sergeant York), Jimmy Cagney (Yankee Doodle Dandy), Fred Astaire (The Sky's the Limit) and the object of Humphrey Bogart's affection in High Sierra. All these actors were old enough to be her father. She was also paired with Dennis Morgan, Jack Carson and the above mentioned Robert Hutton in several lesser films. Yet by 1947 at age 22, she was gone from Warner Bros, billed fourth in Two Guys from Milwaukee, and was out of work for over a year since Jack Warner had blackballed her for getting out of her contract legally. She eventually had to sign with the near-Poverty Row studio Eagle-Lion and then did several westerns for Republic. By 1957 (age 32) she did her last film (a supporting role in the Jane Russell bomb in The Revolt of Mamie Stover) and basically retired to raise her family (though she did a memorable episode of Murder, She Wrote in the 80s playing the spinster sister of fellow spinster Teresa Wright). And yet not only was she incredibly photogenic but could sing, dance (and keep up with Astaire) and had a great flair for comedy. Take a look at her impressions of Cagney, Ida Lupino (both of whom she worked with): https://www.youtube.com/watch?v=LH3L2DBPju0
I never felt she did anything wrong. She didn't owe Bogart's Mad Dog Earle anything. That was all him projecting. He didn't see what was in front of him - Ida Lupino's character - until the end. Ironically, when Raoul Walsh remade High Sierra into a western in 1949, Colorado Territory, with Joel McCrea and Virginia Mayo, he had the Joan Leslie-analog character played by Dorothy Malone, actually curry the hero's favor and more actively betray him, rather than just being a girl with a deformed foot.
Speaking of which, two of my favorite of Leslie's former WB contractees, Dorothy Malone and Janis Paige are still with us (and they are older than Joan). I now worry about them. It seems especially in the last couple of years a lot of old Hollywood has past.