The problem with black widow in the MCU is that, given her status as a normal human, either:
A. Tony Stark would give her an iron man suit of her own to always use.
B. The Van Dynes would give her an Ant Man suit of her own.
C. She would steal one of them if neither gave her one.
What makes NO sense is her just running around without a suit. Its quite annoying. Hell Tony gave a teenager a custom suit.
Honestly, id kinda expect she hid a suit somewhere on that planet where she died and faked her death.