The Final Fantasy 7 update to Super Smash Bros Ultimate has officially launched as of December 22nd. It features new fighter Sephiroth and a bunch of other Final Fantasy things like songs, stages, and spirits. One of these is a new Spirit Battle Board, which contains a fight with Shiva, an ice elemental summon character. Given her looks and ice-affinity, in her spirit battle, she is played by a giant Zero Suit Samus and fights on an ice stage full of Freezie items. More importantly to us, Krystal is summoned as an Assist Trophy almost immediately, probably because of her Ice Blast Staff attack.
According to Dinoman96, this is the first Spirit Battle that features Krystal other than her own Spirit Battle. Can't verify that one, but nice to see Krystal popping up in unexpected places. Watch the video to see her in action.
Thanks to Dinoman96 for finding this and memer55 for letting me know. Video by bdcool213.