How the hell do you use Yvonna?

Yvonna, can't keep her alive. She get's one shotted easy. And doesn't do more than about 1.5k damage even though she's maxed out and full jester set with heavy magic attack. What am I doing wrong with her? level 25 all 3-star jester pieces with mostly magic attack and Crit Rate. level 60 Skadia, lvl 8 all abilities, and I've put her in mixed groups with all of these characters to no success without the other characters flat out carrying her: Fammene (equally as useless), Juha, Headless Knight, Yui, Berga, TX-Manticore, Pantheria, Kalina, and Griselda. I've tried coupling her with a few tank characters but if the enemy gets a random shot off, or charges through the tanks, she KO'd. Advice on her build? Can't seem to get her good after investing so much with longing for a hot ice queen.