I wonder if Demetri used Midnight Bliss on Terry and never changed him back.
From a vampire's perspective, it wouldn't make sense to change them back. gameplay wise, they change back due to gameplay balance, but lore wise, Demitri doesn't change back women he seduced. they either are killed if he chooses to completely drain them, or keep them as servants.
SVC is its own reality, so it doesn't interfere with the Garou and KOF lore/timeline. Demitri wouldnt throw away a women he likes, whether they were born female or changed to female.
http://darkstalkers.wikia.com/wiki/Midnight_Bliss
http://darkstalkers.wikia.com/wiki/Demitri_Maximoff
In SVC dimension, would think someone as charismatic as Terry would be kept as a wife/servant. and Darkstalkers characters are tiered higher than SNK and Capcom characters. There's really no one canonically that can defeat Demitri in SVC except perhaps Goddess Athena.
Demitri currently has about 40 servants in his castle, there's no said cap on how many servants/concubines he would allow.
and anyways especially with an open ended genre like fighting games, any realities and outcomes are possible and branch out to their own reality timeline.
and something like CVS Chaos is even more open ended than KOF stories, so anything is possible.