I personally think Liz really needed that slap in the face before she can move on with life, whethere it's with Maki or not. Because until she got this disillusionment from her first love, she will forever hold Sumire in a pedestal no matter where she is in her life. Now that hopefully that's shattered, she can focus on whatever life she wants to live.
As for Maki, well, she's been allowing Liz to railroad her this entire time.. so..