My earlier answer was obviously wrong - I should have read the Bulette description.
But after thinking about this, i think the fighter may well be able to attack.
I'm not sure though. Here's waht I'm thinking:
The fighter gets its Immediate attack "whenever a marked enemy that is adjacent to you shifts or makes an attack that does not include you".
The Bulette moves as part of the Bite attack, so the question is: is the move a separate action, or is it part of the bite attack? If the latter, then the fighter can attack it. (Since this is not on OA, it won't stop the bulette's move. The fighter would attack as the bulette leaps away, and then the bulette continues its attack normally.)
That also raises the question: if someone charges, does that count as an attack, when the attack is not adjacent, but the move is.
I think, on the whole, it's better to assume the move is separate and so doesn't trigger the attack, but it's food for thought.
But after thinking about this, i think the fighter may well be able to attack.
I'm not sure though. Here's waht I'm thinking:
The fighter gets its Immediate attack "whenever a marked enemy that is adjacent to you shifts or makes an attack that does not include you".
The Bulette moves as part of the Bite attack, so the question is: is the move a separate action, or is it part of the bite attack? If the latter, then the fighter can attack it. (Since this is not on OA, it won't stop the bulette's move. The fighter would attack as the bulette leaps away, and then the bulette continues its attack normally.)
That also raises the question: if someone charges, does that count as an attack, when the attack is not adjacent, but the move is.
I think, on the whole, it's better to assume the move is separate and so doesn't trigger the attack, but it's food for thought.