No, this isn't a BUR for a change - the gabby_(disambiguation) alias has already been made. I've just spent a bit of time cleaning it out, and for once I managed to find citations of ownership for every character in the search results, and even a few pre-existing tags.
The one exception is this character:
Currently, the tag consists only of 74 posts of that particular Gardevoir, and I cannot find out anything about it whatsoever. All clues lead to dead ends or "Commissioned by Anonymous". And yet, if the chatter I encountered along the way in e621 comments and Twitter replies is anything to go by, this character is quite well known (as you might hope, with this much art).
Does anyone have any ideas for what the canonical character tag should be? The owner apparently prefers to remain secretive. The only halfway interesting lead I found was this Twitter user who appears to draw Gabby a fair bit, including some pictures not in those search results, without ever stating that they were commissioned by someone else. But even that isn't definitive. (Their tag on here is normana, for what that's worth.)