In regards to Beth [spoiler]she was very much hurt and angry at Quentin when she found out he was going to marry Angelique. Petofi stopped her from shooting him. Wanting to put Quentin behind her, she decided to work for Petofi.
Though obviously her heart really wasn't in it when she realized Petofi was plotting against Quentin (not realizing he was planning to steal Quentin's body). As badly as Quentin hurt Beth, we see she never really stopped loving him as she ran out of the mill and runs to his side at Collinwood, hoping to save him.[/spoiler]