I know he didn’t stick to the plan when she sent him after Snow, but what with her having his heart in a box now, she probably knows she can trust him to follow orders, coz if he doesn’t, all she’s gotta do is squeeeeeeze. She could tell him that this is a chance to redeem himself, maybe even tell him she’ll set him free if he does this one task for her.
Edited to add that I could see EQ thinking that poor, heartbroken, angry Belle would be vulnerable to the Hunstman’s charms. If you get offered a rebound romp with that beefcake, you don’t turn it down, just sayin’. 😉 Belle would totally take the bait and walk right into EQ’s trap.