Actually, they began Rafe's "feelings" for Hope long before Bo returned. This is why Bo felt Rafe would easily be the one to keep an eye on Hope, take care of her. He never said a word to her, she was in a romance with Aiden, he was her work partner, period.
What has been written badly is Hope's reactions to Bo's return and death, her immediate resumption of her relationship with Aiden. That all just did not ring true at all for her. And then, when Aiden was "dead", her attention was on Rafe. The writing for Hope was dismal, just not the way the Hope character would have acted.
And to add insult to injury, Aiden is brought back, lying thru his teeth again, Hope buys it all without even the flick of an eyelash, and turns away from Rafe again. And not til she learns the truth, does she make that fast turnaround again. Surprised she has not gotten whiplash yet.