What breed and how old is she?
When and what was the last thing she ate?
Is her tummy distended at all?
Any other symptoms...lethargy, fever over 103, etc?
Is she still drinking?
Was there onions and/or garlic in the meatloaf? If there was these are toxic to dogs so you will need to give your vet a call to see if they would like to see your girl for supportive treatment. If not, you can give her some plain pepto bismol to help coat her tummy. The published dose for Pepto is 1 - 3 mg/kg DIVIDED over the course of the day. Using the middle of the range, this is the equivalent of about 1 ml/lb, but this should be divded over the course of the day, One teaspoon = 5 ml; 1 table spoon = 15 ml. You can continue to offer her the chicken and rice mixture and you can also give her plain pedialyte to keep her hydrated via dropper if necessary. :)
I hope your girl feels better very soon, but if she shows other symptoms or does not feel better by tomorrow, I would have your vet check her out. :)
You're very welcome and do let me know how you make out with her. :) Thank you so very much for the bonus...it is greatly appreciated. :)