My Man Godfrey is my favorite film of all time. I love William Powell. I love the ending.
It’s not a screwball comedy but the endearing Powell & Pressburger,* I Know Where I’m Going*,is also first rate.
If she likes this, and she probably will if she has the good taste to like Nick & Nora, she might enjoy Casablanca and other Bogart movies, especially the ones with Bacall. African Queen holds up really well, too. And from there she might enjoy the Spencer/Hepburn movies.
Is Hart to Hart on DVD? I see there are a bunch of snippets on youTube, see if your kid likes them.
I’m watching the pilot episode now, which I’d never seen previously. The tone is quite a bit different from the rest of the series (or at least how I remember it), so don’t let it throw you.
His Girl Friday is one of the funniest movies ever so I’ll second (or third or fourth) that one, and add that the original version (The Front Page) is pretty good too.
More suggestions- Nothing Sacred (an early Technicolor film) and Ruggles Of Red Gap. Both are very funny and available on YouTube.
To condense everyone’s suggestions: find a list of great screwball comedies and have at it. And if she wants a modern film with the true screwball flavor (and hey, it’s seasonal!) there’s The Hudsucker Proxy. You know, for kids!
As soon as I saw “The Hudsucker Proxy” that line went through my head. 
The Hildegard Withers movies featuring Edna May Oliver and James Gleason are funny in a lot of the same ways.
Hmmph… not finding them listed on NetFlix though.
Those were the same two I was going to recommend.
Hopefully she doesn’t get distracted easily. You’ve really got to stay on top of the dialogue with those movies, but they are fun to watch.
The Miracle Of Morgans Creek
one of the best.
All these are excellent movies, but I do think The Thin Man series is unique.
There’s the Blondie series of movies from the 1930s and 1940s, based on the comic strip and starring Arthur Lake and Penny Singleton. Those are pretty fun.
I need to say this very loudly - THE THIN MAN IS NOT A SCREWBALL COMEDY. Screwball comedies are pretty much by definition films in which the leading man and woman are kept apart for farcical reasons only to fall into one another’s arms in the end. You can’t have a married couple be the lead. I love screwball comedies, but the this ain’t one of them.
The Thin Man series are comedy mysteries, which is a different genre. Wikipedia has a handy list of some comedy mysteries. They keep being made, unlike screwball comedies, which died with WWII.
I’m positive a 12-year-old wouldn’t be interested, but since others here might be, let me mention that the closest thing in print to The Thin Man was the Mr. and Mrs. Northseries by Francis and Richard Lockridge (although they are completely sex free, though otherwise adult). A movie was made; all you need to know about is that they made Gracie Allen the lead. I suppose it qualifies as a comedy mystery, except for not being funny. (She never was away from George Burns.) But a 12-year-old might think so.
I didn’t see anyone claim it was a screwball. The movie has much in common with screwball comedies: Emphasis on wit and slapstick, lots of references to wealth and drinking, hyperbolic scenarios, etc.
The plot isn’t the same, but the tone of The Thin Man is very similar to the tone of “The Awful Truth” and similar movies.
Then you didn’t read the thread very closely.
And most of the suggestions are classic screwball movies.
Of course, unless DSeid comes back and gives us some indication of why his daughter liked the movies, maybe we should be listing movies starring cute dogs. Asta - real name Skippy - has his own IMDb.com page.
Or maybe I read it with a different set of thoughts and attitudes than you did.
The Awful Truth, with Cary Grant and Irene Dunne - Irene thinks Cary is cheating on her and files for divorce. Then Irene and Cary go to great lengths to sabotage the relationships the other one has.
Another Irene Dunn/Cary Grant movie - “My Favorite Wife”. Dunn is lost at sea and presumed dead. Seven years later, Cary is having her declared dead so he can remarry, when she shows up, having been stranded on a deserted island with Randolph Scott. Hijinks ensue.
StG
It doesn’t matter what your thoughts were. The words are there, in black and white electrons.
Ah, Gary Cooper. Pretty adorable in this one (and Mr. Deeds).
OP, a number of these movies are available through Netflix and/or Amazon, including “The Awful Truth” which I made my husband watch last weekend and he found it pretty entertaining (I’ve had that “Gone with the Wind” song in my head ever since). We watched “Bringing Up Baby” a few weeks ago, so we had them in the wrong order for the “Jerry the Nipper” gag.
I think most of us know that The Thin Man isn’t a screwball comedy. But we felt that somebody who enjoyed The Thin Man would also enjoy some of the better screwball comedies. As jsgoddess noted, the plot outline might be different but the tone is similar.
Thanks to all. I’ll check to see what is streamable for her.