The singer turns 22 today and will ring in her birthday with a very “private and intimate” bash thrown for her by her boyfriend, Dodger Matt Kemp, sources tell E! News exclusively.   According to the insider, Kemp originally wanted to throw Rihanna a surprise party, but eventually Rihanna caught on and now knows there will be a small get-together. E! News has learned that the party will be a low-key night with Kemp and Ri-Ri’s “closest friends, good Jamaican food, a photo booth, dancing and a nice cake.” Party spies tell us the event will be held at a private residence in Phoenix, where Kemp is currently staying for spring training and where Rihanna arrived to yesterday from Australia to be with Kemp.