1. I noticed in the interaction it's all very proper; even though the characters are attracted to each other, Jeanette MacDonald is trying not to be. Nelson Eddy doesn't mind flirting, as seen when rowing, but MacDonald seems unwilling to admit to herself that she might like this working class guy. When she tries to sing in the saloon, it's clear she's really uncomfortable; this is not the environment she is used to. Nelson Eddy just strolls into the saloon, it's obvious when he walks in with a girl on each arm that he has been in a saloon before.
3. The male/female relationship seems to be that the woman is very proper, maybe sheltered. Rose-Marie doesn't seem to have ever had to had to work before; otherwise why would she be trying to get a job singing in a saloon? It's obvious she's never even been in a bar before. This is what the film code did, she's very proper. On the other hand, Nelson Eddy's character has obviously been working most of his life; he's in uniform, and doing manual labor when we first see him. Even though he flirts with Rose Marie, it's obvious that he's not too serious about her, he admits using his song to try and charm other women. When we seem him in the saloon, he has women on either arm; but he chooses to go after the well-bred Rose Marie instead of staying with the women he escorted in. The message seems to be that a woman can get a man if she's not too forward; after all, the woman with "pip" is left in the saloon