"Heheh, I remember when I had to learn to use four legs," says the Eevee, apparently not aware Swift can understand him. Then, his body tenses up and he gets a look of surprise with a touch of pain on his face. "Eh..agh!" He shudders once or twice and then his body is obscured by the bright glow normally indicative of evolution..but it doesn't look exactly right; it clearly has some odd colors swirling around, particularly crimson and blue with a few bits of violet, and a more pronounced version of the dark mist from earlier in a few places.
The Eevee's mouth is open in what might be a scream if it were audible. The body obscured by the glow grows rapidly into a humanoid shape, followed by the Eevee's muzzle pulling in and a tangle of loose hair appearing around the face. Then the ears grow slightly longer, and the tail gets much bigger, as if scaling up to the body's size. The body's shape changes from androgynous to feminine, the hips pushing out and the stomach pulling in, the arms and legs looking slim, and finally the chest pushing out into breasts, not oversized but clearly present.
"--aaaghh.." The glow dies off, and the tail end of a scream can be heard in a high, girlish voice as
the Eevee's new form* is revealed. She almost instantly collapses. "Ugh."
((*--But with the 'shiny' white/gray colors to the fur and clothing; eyes are the light brown seen there. I couldn't find a shiny pokemorph, and really liked that picture otherwise))