I left my DD for about 3 days when she was 15 months. She was feeding a similar amount, maybe a little less. I found that she was absolutely fine, I know you would be away longer but I wouldn't worry her diet should give her everything she needs nutritionally and if she is a milk drinker then she can drink that (my DD won't drink cow's milk unless it's a babycino) otherwise just a healthy varied diet is fine. I would repeat what the PP said - you MUST take a pump, not just to keep up your supply but if you don't you will explode. I didn't think of it, I was so busy worrying how DD would go without me. She was fine and I was bursting. By the second night I looked like I'd had a cheap boob job, and by the third day I was getting seriously worried about mastitis. Even if you can't store the milk, pump, pump, pump! And she was BFing again within five minutes of me walking in the door.
And your DD will be fine, so have a great time!