I dunno, I rather liked it. The obvious explanation for her suddenly upping her game is that she's much older and more experienced than riful at being at this power level. That was also her weakness; she had never fought someone remotely near her power level, so the methods she was used to didn't work at all, hence her getting taken to the cleaners by Riful 2.0.
Once she realized that, she adopted a form that she had used more often in fights against equal or superior enemies, that of her original claymore form, and using the same strategies from that experience(IE, DODGING...silly awakened being...) in combination with her ludicrous power level, she'd easily destroy Riful 2.0 who has the power but not the skill or the strategy.
I do think that Riful 2.0 has a different reason for existing though. What is that black stuff, anyway? Even if Riful is dead once and for all(nooo! She's my favorite character xD)(I was just happy she came back again!) The black ooze will likely be largely unharmed.
Current theories; Ooze gets absorbed by Clare; Or, Ooze reforms into Teresa, Clare reveals she absorbed the Twins' power and levels up, and the two of them take down Priscilla once and for all!
Honestly this manga has so much up in the air at this point that it could literally go anywhere. It could continue for another 50 chapters(maybe if priscilla gets away, they go to the mainland, join the war, etc...) Or it could end in 2-3 chapters!(Kill awakened beings, kill priscilla, looking towards the uncertain future, the end).
Super excited for whatever comes next!