At 8 weeks it's not really necessary to give her weaning milk through a syringe.
You should try mixing the KMR (kitten milk replacement) with canned kitten food or mashed dry food. While at her age she should be able to eat dry food, if she doesn't, try adding some hot water to it, letting it soak until it's mushy and then mash it up while adding some KMR to it.
And, I would have her seen at your vet's office. She could very well have worms, which could explain the lack of appetite. A kitten that age should have a fairly healthy appetite, and if she doesn't, I would say that's a cause for concern that you should look into.
If she has no appetite towards any food you give her, take her to the vet for a check up. While you are there, ask about Science Diet A/D
. It's a canned food that is generally given to dogs and cats in recovery from a major surgery or illness or to promote weight gain. However, it is highly palatable and I used a few cans of it when I was weaning my first cat, Gerona. Gerona was VERY difficult to wean and at first, all I could get her to eat was the A/D. It's something worth looking into.
First and foremost, though, I would take her to the vet--she needs to go, anyway, for a worming and vaccinations. So, it's like killing two birds with one stone.