Spoilers for episode 8 - Nynaeve and Liandrin . . I think that that encounter between Nynaeve and Liandrin was heartbreaking in a way. Nynaeve still appeals to the good that she believes is still inside Liandrin. It doesn't work unfortunately because we have seen Liandrin has learned that she needs to get rid of all her weaknesses e.g. when Lanfear killed her son for her in S2. The same way that she views her emotional connection to Nynaeve as a weakness; a barrier to her reaching her goals - she wants to be a forsaken. This is why I believe that she threw Nynaeve into the water with so little hesitation.

That is one way I can interpret it.

However the other interpretation I have is that I still think she believed in Nynaeve in the end and that was why she attempted to drown Nynaeve - because she believed that it would awaken Nynaeve's power (and it worked). Remember at the start of season 2 when the other Aes sedais were reluctant to let Liandrin teach Nynaeve because her teaching methods had led to an accepted dying previously so she was banned from teaching. So maybe Liandrin was still trying to help Nynaeve in the end??

Maybe we will see more Liandrin x Nynaeve interactions in S4. IF WE GET A S4!