Miss Smith agreed with defence counsel Greg King in court today there had been an upset between her and Sophie (22) when they were on holiday in Australia in November, 2007.
She knew Sophie was missing Weatherston. She also missed her mother but they sorted their differences and continued travelling together.
She was aware Sophie had a sexual relationship with an Australian man she met on the Gold Coast and also with a Dutchman who was possibly going to visit her in Wellington the next year when she was working at Treasury.
Asked if she knew about Sophie's involvement with a married man in Dunedin, Miss Smith agreed she did.
It was not often someone would say their boyfriend had told them he was ''far too good'' for her and that she was ''very lucky to be seeing him as he was so much better than her'', Miss Vanderwater told the court.
From what she saw of Sophie, the relationship badly affected her self confidence.
Earlier, Miss Smith said the relationship between economics tutor Weatherston and Honours student Miss Elliott appeared to be one of emotional extremes - either extremely happy or extremely unhappy, Sophie's best friend said today.
She told defence counsel Greg King the relationship seemed to her to be either all on or all off.
She had advised Sophie against the involvement as she thought it unwise, given Weatherston was one of Sophie's teachers in the economics department.
But she agreed, apart from one incident when she saw her friend upset because of Weatherston's failure to turn up for an appointment, everything she knew about the relationship came from Sophie.
She recalled Sophie's comments about being sexually dissatisfied with Weatherston - ''on many levels'' - and agreed her friend could be ''fairly graphic'', even talking about the size of body parts.
Sophie had also discussed her relationships with other partners and Miss Smith agreed she was perhaps making comparisons ''in a roundabout way''.
She was not aware of Sophie talking about assaulting Weatherston. But she was ''vaguely aware'' of something she said about attacking and scratching a former partner.
Miss Smith is giving evidence on the fifth day of 33-year-old Weatherston's trial for murdering Miss Elliott (22) on January 9 last year.
He stabbed or cut her 216 times but denies a charge of murder. The defence argues for manslaughter, which Weatherston has admitted, on the basis of provocation from the emotional pain of the relationship and Sophie attacking him with the scissors.
The case is expected to take about three weeks and is being heard by Justice Judith Potter and jury in the High Court in Christchurch.
