My dog is a 4 year old lasa apso and she isn't eating so only eats a couple of biscuits every now and then and she is getting very very skinny what can I do

What all have you tried to feed your dog?
Brands of dry and canned dog food?
And what people foods?
I'm asking because Biscuits sound kind of like a last resort.

If this has gone on long enough for you to notice significant weight loss then it is past time to take her to the vet. Healthy dogs do not starve themselves you need to find out if there is something wrong with her medically.