Gabriela Irimia, of pop duo The Cheeky Girls, has spoken for the first time of her relationship with MP Lembit Opik.
The 24-year-old told GMTV she had been seeing the Liberal Democrat frontbencher for two weeks and their relationship was "really genuine".
Twin sister, Monica, said Gabriela had "never been so much in love" and had "never had a proper boyfriend".
Mr Opik confirmed on Sunday that he had split up with his long-term partner, weather presenter Sian Lloyd.
The 41-year-old MP, who is the Lib Dem spokesman on Wales and Northern Ireland, said the couple had separated "some time ago" and it was "no secret" that he was seeing Miss Irimia.
He assured party officials there was no overlap in the relationships.
On GMTV Miss Irimia hit back at claims by Ms Lloyd that her relationship with Mr Opik was a "pantomime" and that the "affair" had led to the couple's break-up.
"We do know each other from two months, but didn't actually go out together only from two weeks now.
"Our relationship was very platonic at the beginning and we had long chats on the phone.
"We didn't actually meet very often. All I can say is I don't know Sian. I saw her on TV and she is a very attractive woman.
"I could understand the situation because anybody who would come out of a really long relationship would be hurt but I am sure she will be very happy in the end."
She added: "Our relationship is really genuine and it's not out of a pantomime or anything like that.
"We understand each other really well and we are looking for a long relationship here."
She said Mr Opik had been "quite impressed" by the media attention their relationship had generated.
The sisters' mother and manager, Margit, said Mr Opik had been a "little bit shy" when he first visited the family home but he had got on well with their Irish wolfhound dog, Rocky.
Monica said her sister was "dreaming with wide open eyes" and was so lovestruck that she had stopped going to the gym and doing her household chores.
Mr Opik and Ms Lloyd announced their engagement in 2004 and had been together for four years.
The MP said in his statement at the weekend he continued to regard Sian as one of the "brightest, most out-going, hard working and generous people I've had the privilege to know".
"I hope that she will remember the happy times as we both go our separate ways. I wish the very best for her," he added.
The Cheeky Girls arrived in the UK from their native Romania in 2002 and shot to fame with appearances on reality TV shows Popstars: The Rivals and Model Behaviour.
Their first single The Cheeky Song (Touch My Bum) reached number two in the charts in 2004.
The duo faced bankruptcy this summer when Telstar, their record company, collapsed.
But Mrs Irimia promised they would bounce back with a new cheeky girl, the twins' six-year-old niece Lory, singing a new version of the Hokey Cokey.
The trio released a download album in November titled In My Mind (Is A Different World - A Cheeky One).