It's interesting to think about how things have changed over the decades. I used to work for a transit agency, and I remember another (female) co-worker talking about how the guys teased her. Now I think some of the things she reported would have gotten the "boys" fired.
In the 1950s, I think probably teachers and nurses were widely accepted (as Joan mentions) and even the horse librarian's role wasn't challenged. However, I can see why some men resented women in the other two roles (fire lookout and miner), since they were taking "good jobs" away from men.
Of the two, I think Bonnie certainly had the more dangerous job. Not only was she subject to harassment and resentment from her male coworkers, but the job itself was dangerous.