The new tattoos on her shoulder are roman numerals that read "11-4-1986". It’s her best friend and assistant- Melissa Forde’s- birthday! Sources online confirm it definitely isn't Rihanna’s (February 20, 1988) or Chris Brown’s (May 5, 1989) birthday.
Rihanna and also mentioned being accompanied by Melissa anywhere she goes… even the shower:
Here's Rihanna describing how she got off the body paint from the video Umbrella:
The body paint was really oily. I couldn’t wait to get it off my face. That was the worst part about it - getting it off. I was in the shower for two and a half hours! My best friend had to come and shower with me, because after I tried to do it myself, the silver would just go back to where I just washed myself. She was just like, “Take your hands off and let me do it.” ... It would not come off. [Laughs]" (source)
The other "Shhh..." tats are on Rihanna's fingers. .
Looks like she's wearing some extra bling too. A nipple ring piercing was visible through her sheer tank on the red carpet at the MuchMusic Video Awards.
Rihanna hosted a surprise birthday party at the Star Lounge for Melissa Forde, where she showcased some star tattoos at the party that are on her neck and back.
UPDATE: check out more of Rihanna's tattoos here.