Must be vanilla Sora; cannot be gotten from KO'ing Sora (Military) while under the effects of Delta Field.
This can require a lot of setup, or can happen randomly if she happens to stroll in front of you at low hp. Just ensure you're playing with at least 1 Sora, made simple by selecting a campaign level where she is featured, one of which would be QP Episode 5. Pack some battle cards, you'll need them to buff Sham's inherently lackluster attack. Recommended cards would be Big Magnum or Final Battle.