Jack-O is a magical sorta-clone body of Dizzy's mother, Aria/Justice, and has half of Aria's soul, but is in Strive counted as a separate individual with her own individual consciousness and personality.
So... I wouldn't exactly say she is Dizzy's mother.
She's Dizzy mom in the sense that she her dad lover. A step mom. Incest is any form of in family sexual intercourse no matter if they are or aren't blood related.