The bodies of the women who fell into the water at Ystradfellte Falls last week have now been recovered.
Scotland Yard said there was no threat to the public
A Wirral woman, 23, has been held on suspicion of assisting an offender, police added.
Metropolitan Police Commissioner Sir Mark Rowley said the force has ‘a practical plan for turning things around’.
Theo and Remell Bailey are wanted in connection with the 2021 murder of Gavin Parry in Winson Green, Birmingham.
Area coroner Katrina Hepburn adjourned the inquest into the death of 14-year-old Mackenzie Croxford-Cook.
Police were called to reports of a fight in Knotts Green Mews in Walthamstow, east London, on Saturday at about 5.08am.
The two women were found by officers having suffered stab wounds at a residential address in Windmill Lane at around 3.35am on Sunday morning.
Scott-Swaley Daniel Stevens died after the collapse of a garage wall at a property in Clacton on Friday.
Fay Johnson will appear before Bristol Magistrates’ Court on December 15.