Girls Aloud star Nicola Roberts is engaged. The 38-year-old pop singer is set to marry businessman and semi-professional soccer player Mitch Hahn, after she showed off her sparkling engagement ring at Brighton Pride over the weekend. A source told The Sun newspaper: “Nicola has met her soulmate in Mitch. She couldn’t be happier.” The loved-up couple have been dating for the last two years, and Mitch is thought to have proposed during a recent holiday in the south of France. Nicola performed alongside her Girls Aloud bandmates Cheryl, 41, Nadine Coyle, 39, and Kimberley Walsh, 42, over the week…