The 21-year-old was showered with gifts including a bottle of wine, chocolates and long-stem roses - given to her mainly by the media - during the first full day of her promotional tour.
The Barbados-born, US-based singer was suffering from jetlag and needed a midday sleep to get through her commitments, but said she was used to spending special days working.
"There are sacrifices," Rihanna told AAP.
"I shot (the video for) SOS on my 18th birthday.
"It doesn't bother me that much because I know I have to make sacrifices to make things happen. This is important to me."
Rihanna is in Australia to promote her latest album Rated R, which was written last year after she was assaulted by her then-boyfriend, singer Chris Brown - a topic journalists were warned not to ask about.
On the album she shows off a tough, powerful, sexy image on songs like Russian Roulette, Hard and Rude Boy.
Rihanna said it wasn't her intention to be deliberately provocative, it just reflected a specific time in her life.
"When my album first came out and people saw the pictures and they heard the songs they would say it's darker and the images are really sexy - I didn't get it," she said.
"I got really defensive because I didn't think so until I looked back at it.
"When I was making this album, whatever came out I wanted it to be real and authentic and natural and just something that was honest."
There is also a softer side to the international star, who spent Saturday visiting the Sydney Aquarium and dining at Italian restaurant Beppi's.
"Hmmm, I like flowers," she said.
"Let me see, I like stilettoes, I'm really into skin care, and I like spending time with my friends and my family. I like giving back, I'm really into charity.
"Those are some of the more vulnerable things about me."
Rihanna is in Australia for just three days, having flown in on Saturday morning from Japan.
She isn't performing on this Australian visit, but will be back later in the year for a series of concerts.
"We're actually going on tour in April," she said.
"We start in Europe and then to the US and then we come back here in October, when it's going to be spring, so I'm really excited about that."
