https://pistol-forum.com/showthread.php?4336-BUG-s-380-ACP-vs-38-Sp
Here's an article which addresses the .380's self-defense capabilities. Please look it over.
-The .380 at least addresses the first rule of gunfighting which is, "have a gun".
-Ammo is a bit higher in price, but ~the same as .38 Special, lately.
-There now are 9mm guns which are similar in size to the .380, which can make them a better choice, ballistically, than .380, but you've already mentioned "shot placement matters".
-To answer one of the questions, no, I've not handled the LCP .380, but it generally looks like a good weapon, especially for the price you can get it. On a related note, I wouldn't consider Glock's 42, as there are just too many reports of feeding/reliability issues.
Here's yet another link to get some ideas for your fiance. It's a woman who is a firearms advocate who carries all the time:
https://www.facebook.com/LimatunesRangeDiary/?fref=ts
It may provide you with more ideas and a perspective of what's involved. I believe she's currently carrying a 9mm S&W M&P Shield, but these things change over time. As you'll see, she's a bit on the smaller-side.
Summary.
Choose a reliable weapon in 9mm and go from there. With the weapon choice, decide on means of carry, meaning think of the weapon and handbag/holster as a system, as in, don't buy a handgun and then find there are no likable holsters available. Budget accordingly. While the initial price of the LCP .380 may be $200, with a 1,000 rounds of ammo and a handbag/holster the total cost can approach $1,000 quite easily.
Who needs 1,000 rounds? Isn't that excessive? In the short run, shooting a mere 100 rounds each time for practice, that's only 10 range visits, which will only make one better with that firearm. One may even consider herself an "expert" with that firearm. By expert, that can just mean better than before; better than some; but not necessarily better than others.
I forgot to say, "CONGRATULATIONS ON YOUR UPCOMING MARRIAGE"! Let us know what you decide to buy