that depends on how long it is, whether it is chest or full body, this girl's chain is full body and extra long at that.
I may have shot a bit over the top, but 20kg is also way to little.
and 20kg by the way is also more than an average girl can carry.
Chain mail is freaking heavy, it is not just a fashion statement.
But I guess if instead of using iron we use some kind of fantasy material like mythril, that is half as light as aluminium and trice as strong as steel, than sure she can carry it.
It still wont help her in a sword fight though, as physical strength is the most important attribute, not simply due to the strengt needed to swing that fancy sword of hers, but also to absorb and direct blows.
Its a fact that is often ignored in RPG's, but there is a reason why women are never seen on the battlefields.
To be honest it is a beautiful painting, but I don't like paintings that lie.
Get her out of that silly outfit and put her in a beautiful dress.
There were reigning queens in the middle ages, but they didn't get to their position by pretending to be a man.
One of my favourites, were Queen Margaret I "the lady king" daughter of Valdemar IV and founder of the Kalmar union.