What can she really do at that point? From her perspective, Conan won't give in (reasonable considering she came off as very hostile and untrustworthy during this case), but she got information that Ai Haibara appears to be like Conan, so there's her next point to be investigated for the future.Also, Sera just gave up or what?
Nah, he obviously knows the cornerpoints, but he has been repeatedly changed stuff up during production and added additional aspects. So it's not like he has a set in stone plan on how to exactly proceed with the BO plot.From some interviews I reckon that Gosho already has the whole story concerning the black organisation planned out.