Vivian was dimwitted so she won't be able to tell that Elara was Olcan's mate especially because she was clouded by her jealousy but what of Seline?, the girl was proud and egoistic but her mind was sharp, it won't take time before she pieces one on one together and discovered the truth.
Jacob was right too, what if Vivian had told some other people then what would they do, they can't keep just blocking attacks for Elara, it would even make people suspicious quickly. For example if Olcan kept intervening in Seline scheme against Elara it won't take more than two trial before she would know that Elara and Olcan were mates and once she knew...Tsk it's equivalent to the whole realms knowing and that was just what they had to avoid.
"So what do we do?" Marcus asked. As for him and Marzen they held a different worry in their minds.