Rigged her hair. Also rigged her rifle with bones for the trigger, clip, sight, upper and lower parts of the barrel, and the 4 panels around the barrel so you can pose it to look like she's firing her Ult. The barrel should only use X Scaling for that so I locked everything else on those two bones.
Update: Fixed geometry and weight mapping on her collar. Also changed her wearable preset to begin with 02 like it should have originally. Delete the Black Widow outfit in Daz starting with 03 if you are updating from the previous version.
MR Black Widow: https://mega.nz/file/QXUimBRQ#FFQt-emIrORzx08mttTr3uuexdrcKZE6zBjnGWET8og