I'd definitely go with BB since blooming her adds 1.2x skill proc rate for the entire squad and, if I'm reading her 'new' first ability right, adds an attack power buff for the entire squad (+10%) in addition to supercharging attack power for herself and a random squad member (+50%, so +60% total for BB and the squad member).
All blooming would do for Setaria is increase her own power (better stats and the additional ability to counter attack 80% of the time); the attack boost for the squad stays the same (+14% for Setaria and two random squad members) as does her chance of evading attacks.