All-in-all, I feel like this is, in its current state, a bit short and mundane. The writing is interesting, but doesn't really lead to anything of note. I'd personally suggest an Interview Log before time of death to flesh this out a bit more, and maybe expand on some ideas presented here - particularly recovery and testing procedures carried out while examining the transformation process, which I'm assuming was done based on some writing here but has no concrete description.
My biggest gripe with this article is that this feels well out of place for SCP. It's a girl with a horse head. While I can definitely see the Foundation containing some more mundane anomalous objects, the presentation and idea currently in this article seems much more at home in a Circus Side-Show rather than in the safekeeping of a secret global organization.
Something with some sort of stake - even if the stakes are relatively low compared to the rest of the Foundation - would do this a world of good. Why is it that the Foundation needs (or needed, I guess) to keep this contained? What is so dangerous, anomalous, strange, eldritch, or otherwise "risky" about it that required the falsification of a disease, forgery of death certificates, and isolation of the event to a maximum security secret facility?
Alternatively, if the Foundation didn't need to contain this, that's information that might be interesting to expand upon as well - more specifically, why the Foundation felt like it had to.
Otherwise, I can't really see containing this any more than I can see the containment of Elephant Man, given the presentation that's here now.
Edit: Small formatting error
I can't really tell what's going on here - this is a really heavy oxymoron. As written, it seems to be saying that when her hair is down she's back to normal… But then immediately states that she can't go back to normal ever. I'm assuming you're trying to state that the changes can't be reversed while the hair is up, or that the changes while hair is tied are gradual and those gradual changes stop occurring when hair is down. Even then, I not so sure on that.
The changes stop when the ponytail is down, but they can't be reversed. She does not become normal. What has been changed can't be unchanged.
Also, I've corrected and emboldened some spelling mistakes.
Those were not spelling errors. Those were the writing of the Commonwealth. I prefer my English to be British.
This document/section isn't currently written in.
I'm referring to that very article itself. It is logically the main description of the SCP's physiology.