I woudn't get too worried just yet meowmie. I'm glad she has a vet appointment tomorrow though so you can dicuss all the problems with them.

If you are giving her the same food that she was eating before then problems shouldn't be from a change in diet. I always mixed canned food with a little dry to get them going but you have already done that. I'm sure a lot of the problem is stress and being taken away from her momma. I have always thought they should stay with mom until they were at least 8 weeks old but that's just me. Most people pull them earlier.
One thing that most of us have found kittens can't seem to resist is human baby food. Chicken or veal baby food really seems to appeal to cats and kittens. That's how several of us got some pretty sick kittens eating. You might want to give that a shot. I gave straight baby food for a few days then began mixing it in the dry food and slowly weaned them off of baby food.

Keep doing what your doing until the vet visit tomorrow. I'm sure she needs to be wormed as well. She will be fine until then. Give her lots of love and make sure you keep us posted on how she is doing.