Rihanna doesn't have many close girlfriends, which her pal Cara Delevingne thinks is because they don't understand her. Cara Delevingne thinks women don't "understand" Rihanna.The British model struck up a friendship with the 'Diamonds' hitmaker two years ago and says she can always rely on her singer pal to look after her when she visits the US.Cara - who walked in Rihanna's River Island show at London Fashion Week - said: "The Rihanna show was fun."I met her when she was here two years ago doing a gig. And then she sang at the Victoria's Secret show and we hung out."She looks after me when I go to LA. She's the best, she's such a sweet, down-to-earth girl."She doesn't have that many girlfriends but we have a lot in common. I don't think many girls understand her."While Cara enjoys spending time with Rihanna, fashion insiders say people are always delighted to be with the 20-year-old beauty because she is so "fun".Stylist Katie Grand told Grazia magazine: "Of course she'll generate publicity, but for me she's just someone fun to have around.When she had her fitting for Marc Jacobs she squeezed him on the shoulder and said, 'Shall we go for a drink at the nearest gay bar.?' She doesn't do it to get on, she's naturally sociable and fun."