It seems that even celebrity bra-fitter often have no idea about proper bra fitting
Here you can see that Rihanna's bra band is riding up on her back. That means her band size is too large
Here you can see that her cups should be wider. They are cutting into her breast instead of encircling it.
The blue line
marks the place where the underwire should be.
For comparision, this is how underwires should look -- they should end more under the armpit:
Rihanna's only saving grace is young and perky boobs, which hold their shape no matter what they are stuffed into. But by wearing this kind of bra, after some years she will have squashed her breast tissue with the too-small cups, and the fat tissue will migrate and make unsightly buns in the underarm area, armpits and even the back. The straps that ride up will not offer enough support.
So, when we are bombarded with images of ill-fitting bras, no wonder the average girl has no idea how a well-fitted bra should look like !
If Rihanna took a tighter band, and then went up a couple of sizes with the cups, she would get a bra with cups that were not deeper, but certainly wider.
You might also want to read:* the Bra Matrix
* how to measure your bra size correctly
* Buying bras online: a short guide* Does this bra fit ? How can I tell ?
* The tricks we use to pretend that a bra fits
* Bra Myths busted