I am definitely not trying to insult you, but the internet sure has a way of magnifying problems, even genuine ones, with a cartridge. If you were to base your opinions purely on gun forums, you'd think shooting .40 S&W was like holding a stick of dynamite and .380 was a BB gun.
Keep in mind that 9mm short has been a popular European police loading for decades. It gets pretty cold in parts of Europe too, and people wear coats there, too.
Is the .380 a duty cartridge, in the same league as 9mm/.40/.45? Absolutely not. In a full-size gun you're better served with a larger cartridge. But in a small gun, it nicely bridges the gap between concealment and power.
I carry my LCP year-round. I shoot well with it and it wears easily so I am carrying 100% of the time that I legally can.
Her confidence and comfort with her weapon system are paramount. If she trusts the Thunder and is comfortable and familiar with it, her proficiency with the system will more than make up for the .380's moderate performance
Beretta PX4 .40 S&W - Beretta 92FS 9x19 Para - Rock Island Armory GI 1911 .45 ACP - Colt 1968 Detective Special .38 Spc. - Ruger LCP .380 ACP - Daniel Defense M4V1 Carbine 5.56x45 - Ruger 10/22 .22LR - Remington 870 Express Tactical 12GA - 1943 Izhevsk Mosin-Nagant M91/30 7.62x54R