Belle didn't know why Lucas chose Greed to go with her, but she didn't question his judgement. Even Barron and Greed themselves looked confused that Lucas was sending Belle with Greed when Lucas wouldn't be there to protect her if the Sixth Grim were to decide to kill her off.
Before Barron could interrupt, Lucas looked at Belle and placed a hand on Barron to disappear from there.
"Looks like we are going to be spending more time together," there was a sick smile on Greed's lips, his blue eyes looking down at her.
"Too bad that we have ghoul as the third wheel between us," Belle retorted back, her eyes holding barely any humour. She looked at the ghoul, "We should get going," and they left the cemetery with the ghoul disappearing such that one could see only Greed and Belle walking out of the grave.