In the season finale, Will says he forgot his tape recorder because his schedule was off and he had to pack to take Betty to work with him. But the flashbacks of Angie getting taken rely on Betty being at home. Betty is pivotal because Paul smells the killer's lotion, and Betty is the reason Angie didn't get away.
The plan to sniff Betty's fur to ID the killer by the smell of his hand lotion wouldn't work because the killer had gloves on when holding Betty. Except that he had used the hand lotion before he put on the gloves and the scent of the lotion would have transferred.