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This fertilizer looks to be mostly nitrogen. Assuming she had a lick and only ate a small amount (not straight from the bag), then the amount ingested was probably small. Fertilizers are usually salts of nitrogen, phosphorus and potassium (N-P-K, thus the 3 numbers on the bag, e.g. 13-5-8). As such, they are not terribly toxic, but ingestion of a large amount can (as with any excess salt ingestion) cause digestive tract upset (vomiting and maybe diarrhea) that is usually short-term and essentially once they puke/poop out all the irritating salt, the upset stops. The most we might is expect vomiting soon after ingestion and possibly diarrhea, although sounds like the amount eaten was small. I would expect these signs to resolve quickly. If they do not and Shelby develops profuse vomiting/diarrhea, then she needs to be seen on emergency. Then we run into dehydration/electrolyte problems.
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