I never doubted whether she could bulk up or not, I only doubt if she or the producers want her to since being overly slim is considered sexy these days.
With that said she doesnt have much muscle at all in OP's picture so I dont know what point he is trying to make, she simply has a really low amount of body fat which makes the muscle more defined, there really isnt much size going on there at all. Fat levels are all the difference between a bodybuilder and a strongman. Dont think I want her super pumped though, but some more size would be nice.. I'd like her arms to look like this.
I think sometimes people prefer to hire a girl over a boy but usually the people who do that sort of thing also expects personal things from the girl, so its kind of a double edged sword. This probably happens to men too, just not nearly as often.
I think men (boys) have an easier time finding a proper well payed job without unrealistic expectations, atleast when the boss is a bit older and set in his ways.