Even if she was a guy, it's unlikely she'd be readily accepted because she defected. Soldiers generally don't trust "traitors". Her being a girl is just giving them more ammunition for trash talking her. Basically, I don't think her being a woman is the real problem.
As she proves herself, they'll change their mind. After all, I believe King Blondie promotes based on talent. Thus his commanders will be of a similar mindset: when they realize she's truly talented and loyal to the King, they'll set their biases aside and recognize her.