Favorite movie can remember the whole movie, just not the title!

I am looking for the name of a movie that was probably made in the 1940s. It’s about a young girl who is very politically active. She writes letters to soldiers in the war to build up their morale, but pretends to be her older sister. The sister works at a bank and is engaged to coworker. A soldier shows up at the door during his leave to meet the sister. Everyone goes along with the sister pretending to be the one who wrote the letter while the soldier is there, thinking that he will eventually leave. The sister ends up falling in love with the soldier. It’s a comedy and there are at least two more movies made about this family.

Any help would be wonderful. I watched this movie for the first time almost 30 years ago I found it again about 3 or 4 years ago, but forgot the name again! I need to tattoo it on my body somewhere!

Thank you