I would take her to vet as soon as you can. If she is acting lethargic and is trying to vomit and you have noticed her vomiting "left overs" from a toy. With the information you have given me I would conclude that perhapes she has an obstruction. This basically means there is something hanging out in her stomach that isn't supposed to be there. This is what I can conclude by only what you are telling me. It is best that you take her to a vet where a vet can actually look at your pet, in additon, to run a fecal sample (incase she picked up intestinal parasites,) take radiographs if needed, ect. If it was my pet I would take her to the vet ASAP.