You may want to look at the M&P pistol. It has an ambi-safety, good sights and trigger and a very low bore axis to help recoil control.
budsgunshop.com/catalog/product_info.php/products_id/24037/Smith+%26+Wesson+11524+M%26P+M2.0+Double+9mm+4.25+17%2B1+TS+3Dot+Black+Interchangeab

Your best bet is to find a local gun shop & range, Most have a rental case where you can try them out. I took my wife to one and when she found what she like then I purchased it at Buds. Hope this helps.

You're getting lots of good ideas here, so you see you have options. I've noted that the Berretta Storm is "ambidextrous" and that several HK's have changeable controls to make them "southpaw". Also know that almost every 1911 out there either comes "ambidextrous" or a new safety can be easily installed. One of the new 1911 alloy frame/9mm combos would make a great "lefty".

Let her try as many as possible. Let her make the choice.

I would check out the Ruger SR9 and the SR9C they have a ambidextrous Thumb safety the trigger safety also the mag release is ambidextrous the SR9c comes with both 10 and 17 round mags. The 17 rounder has a grip extension that makes it a full size sr9 grip. If you ever have a problem with it Ruger is a great company that stands behind their products. The SR9C is my summer carry gun

Check out the Sccy 9mm with ambidextrous manual safety. 9mm is an excellent defense load and the Sccy 9mm, made in the USA is very affordable and reliable.

I like the CZ 85 myself (Buds has a few surplus still), but I can't argue with the HK USP you're leaning too. If money is not a factor, you have many to choose from. Tough decision for sure. Good luck to you.

It would be wise to find a local gun shop and experiment for the best fit firearm specific to your personal needs.