The mother of murder suspect Shauna Hoare joked with her that she was hiding from police because she had kidnapped missing teenager Becky Watts, a court heard.
Lisa Donovan became suspicious after her 21-year-old daughter began spending so much time at her house after having no contact with her for nearly four years following an argument over a car.
Bristol Crown Court heard Hoare started a relationship with Nathan Matthews, who her mother described as "controlling and flirty with everyone, sexually oriented, very overpowering", at the age of 14.
Mrs Donovan explained that the pair rang up out of the blue on February 23 - four days after 16-year-old Becky died - and arranged to visit that night, returning over the following days.
Meanwhile, as part of inquiries into Becky's disappearance police were making attempts to search Matthews and Hoare's rubbish-strewn home at Cotton Mill Lane, Barton Hill, Bristol.
Mrs Donovan said after several visits she teased her daughter about knowing the missing teenager.
"I was joking because I found out she knew Becky," she told the jury.
"I said 'I know why you are at my house all the time - because you are running away from the police because you kidnapped her'.
"Nathan wasn't there. At first she just asked me how I knew she knew Becky. She said 'no'."
The mother-of-eight described the night the pair turned up out of the blue.
"Nathan was the same old Nathan. Shauna was what I was expecting," she said.
"He was wearing her down. She wasn't like what she was when she first met him. He was very controlling."
She added: "He seemed alright as a person but I didn't like him with Shauna. He just didn't seem to have changed one tiny bit. He was very flirty with everyone, sexually oriented, very overpowering.
"He would make sexual comments all the time. He rubbed himself against my other daughter."
Prosecutors allege that Becky was killed at her home in Crown Hill, St George on February 19 and taken by Matthews and Hoare in their car to their home where her body was dismembered in the bath over the following days.
As the police launched a missing person inquiry, prosecutors say the pair set about covering their tracks - telling detectives they were going out for a meal on the evening of February 23 with Hoare's mother and step-father and were staying away that night, so would not be able to let them in their house.
Matthews phoned Kevin Stone, Mrs Donovan's partner, to ask for a favour.
"I thought it was a bit strange. He said 'If anyone comes for me can you tell them that we are going out for a meal because we are supposed to be going out with someone and don't want to'," Mr Stone said.
Prosecutors allege that it was that evening they in fact returned to Cotton Mill Lane and planned the removal of Becky's dismembered body to the shed in the garden of their friends Karl Demetrius and Jaydene Parsons' home at nearby Barton Court.
A work colleague of Karl Demetrius and Jamie Ireland told jurors that the two men carried out a "job" on the night the teenager's remains were moved.
Nathan Bignell, who worked with them at a firm contracted by Airbus at their site in Filton, Bristol, told of a conversation he overheard Demetrius having with Ireland.
"The job was collecting or delivering something and they would get paid well for doing it. I'm not positive who was on the phone but I heard his brother's name mentioned," he said.
When police did successfully look around Matthews and Hoare's home the following day, they found the house full of rubbish, piles of clutter and smelling of cat poo - but the bath was clean.
Matthews, of Hazelbury Drive, Warmley, South Gloucestershire, denies murder and conspiracy to kidnap.
He has pleaded guilty to perverting the course of justice, preventing burial of a corpse and possessing a prohibited weapon.
Hoare, of Cotton Mill Lane, Bristol, denies murder, conspiracy to kidnap, perverting the course of justice, preventing burial of a corpse and possessing a prohibited weapon.
Donovan Demetrius, 29, of Marsh Lane, Redfield, Bristol, and James Ireland, 23, of Richmond Villas, Avonmouth, each deny a charge of assisting an offender.
Karl Demetrius, 29, and his partner Jaydene Parsons, 23, both of Barton Court, Bristol, have pleaded guilty to assisting an offender after the teenager's body was discovered in their shed. Both maintain they were unaware of what the packages actually contained.
The trial was adjourned until Monday.