Because of species swaps, we don't set species implications on characters. It looks to me like Silverlay has been drawn species swapped three times.
Okay. It's just that she has 793 images on here, and "not even a tenth are tagged with the umbra pony tag.":/search?q=oc%3Asilverlay%2C+umbra+pony
"778 images currently do not species swap her":/search?q=oc%3Asilverlay%2C+-species+swap, and out of those, "only 36 are tagged as umbra pony":/search?q=oc%3Asilverlay%2C+umbra+pony.