Robin would have told Sabrina. Even if not openly because of Devin, then in private. But she was pregnant and it would not be right for her to have panic attacks in the fear of someone being after her life.
Robin had already made the mistake of hinting to her at the party to be careful and not eat anything.
His only ambition now was to clear that on her mind, so she wouldn't live in fear. Behind her back, he would deal with her enemies.
"She won't talk. It's the reason why she ate the food and she looked fine when we let her go."
Anyone should be able to interpret Robin's words to mean there was no poison as he perceived but not Devin.
"It means that somebody wants my sister dead. What if it's that stupid girlfriend of yours," Devin said.
Robin was very annoyed by Devin's presence and words but tried his best to endure it for Sabrina's sake.