Belle is going to stay loyal to Rumple because that is the type of person she is. However, what if Hook makes Rumple think that Belle is straying? Rumple has self esteem issues and Hook has a history of stealing Rumple’s women so to put that thought in Rumple’s mind isn’t going to be too hard.
Rumple’s going to face a dilemma. If he says nothing to Belle, his paranoia is going to continue to grow, but if he does say something to her then she’s going to be offended that he thought she would cheat on him.