Re. Weapon Request: Her "legs" look like Jak-3 elements. The gun should be a UB machine gun. It's modified for handheld use by a superhuman.
The UBT and UBS guns were used in AA role, when Duschkas got rare:
https://topwar.ru/uploads/posts/2022-05/bt-na-trenoge.jpg

The barrel is too long and looks more like a ShWaK, but that one has its gas cylinder under the barrel and a almost cylindrical receiver.