Source: Bang Showbiz, Photo: ReutersRihanna is not concerned about Chris Brown's recent meeting with his ex-girlfriend Karrueche Tran.The 24-year-old 'Diamonds' singer reportedly trusts the R&B star - who was spotted out and about with the model in Los Angeles on Monday (22.10.12), despite having ended their relationship last month in order to rekindle his romance with her - and doesn't consider Karrueche a threat.A source told HollywoodLife.com: "She trusts Chris so whatever he had to do to get this girl out of her life, she got his back. She supports him on it and that's her business. She's not tripping off the small s**t anymore. F**k that, life is too short."Now, if that was Rihanna some years ago, she would have let [Chris] have it. But over time, you grow up...That girl is his ex and I'm sure she knows they got to handle s**t after they break up and all that, so it's cool."So yeah, she [trusts] him and no he [isn't] f**king around on her. And if you really want to know what's up, she never thought this girl was a threat or anything like that. She barely even knows her name. She's never even brought up and [Rihanna] could really care less. She know where Chris' heart is and that's all that matters."The 23-year-old 'Turn Up The Music' singer - who recently reconciled with Rihanna despite still being on probation for beating her in 2009 - was spotted leaving his home with Karrueche before driving away separately. However, they met up later on and were spotted sitting in the same car, reportedly on their way to a studio in Burbank.