I identify with your gf. I am sort of the same way. I didn't grow up with lots of love. I grew up hearing more hateful words than love. I can count on one hand the number of times my parents told me they love me. There were no hugs or kisses either. Because of that both my sister and I dated men who put us down or were verbally, physically, or mentally abusive.
I struggle with this now and more than anything I want to be the girl that is warm and loving, don't get me wrong I'm not cold and uncaring. I express my affections through actions (doing nice things for people, much like your gf doing your dishes) rather than through words. Saying "I love you" is the hardest thing in the world for me to say because I feel like it makes me vulnerable or something, very hard to explain.
I am getting better with this in my current relationship. It just takes time and a man who can be patient with me. If you say something to her she may feel attacked. I think the best thing you can do is let her know you are appreciative of her. I think she will eventually let her guard down and start to reciprocate. I may be wrong though. Maybe she is just the type that shows her affection through actions rather than words. I know there is some sort of book out there my friend read before she got married. Its a quiz of sorts where it tells you how you express your love and how you like love to be shown to you. That might be something you'd want to look into, it may be a way to break the ice with her without her feeling attacked.
So, so you think you can tell Heaven from Hell,
blue skies from pain.
Can you tell a green field from a cold steel rail?
A smile from a veil?
Do you think you can tell?
And did they get you to trade your heroes for ghosts?
Hot ashes for trees?
Hot air for a cool breeze?
Cold comfort for change?
And did you exchange a walk on part in the war for a lead role in a cage?