Like her real life counterpart Stevie Nicks, Daisy impulsively marries after a traumatic event. Nicks married her best friend's husband in grief after her friend died of leukemia, while Daisy marries Nicky after being betrayed by Billy.
In the book, Daisy's husband Nicky is a controlling, abusive Italian prince. However since Italy has no royal family, the implication is he's a con man, which is noted by the band members. On the show, Nicky is Irish instead of Italian and while his royal status is still debatable, the series doesn't dive into his questionable or abusive con man behavior.
Daisy's husband Nicky is based on the con artist Count Jean de Breteuil, drug dealer to the stars in the 1960s and 1970s. An alleged member of the Parisan aristocracy, he dated and supplied drugs to singer Marianne Faithfull like Nicky does with Daisy. Breteuil would die at the age of 22 in 1972.