>>53726090I mean, you could just try and search her name or the comet emoji on pixiv while setting the search function to title/captions only instead of the tags.
Following artists who doesn't upload their stuff with the fanart tag on Twitter also helps, since it allows your feed to catch on whatever other untagged fanart that artist might be following.
this also works with the other kind of fanart if you type hsmt, hsmtsisi, Siちゃん, すいちゃん, etc. 