In Co-op mode, Fernet's stats and passive do not change.
Fernet's Hyper, Air Strike, has a slightly different effect in Co-op. The Hyper will only affect enemies and not players, and only deals 1 to 2 damage.
Fernet's passive and Hyper are unchanged in Bounty Hunt mode.
Fernet's base stats give her 46 starting stars and a discount of -15% at shops.