Welcome to Mytoos and to the world of living with a mature cockatoo. Please take the time to read the forums. Biting has been discussed over and over and consider yourself lucky if you are only being pinched.
Biting is a learned behavior in birds and is resorted to when the other forms of the birds communication is not being heard (body language). Once they learn that biting works as a form of communicating, of course they will continue to use it. It's not the taste of blood, it's the act of biting that gets your attention. If your BF is triggering hormonal behavior then he needs to have a hands off approach until her season passes...their natural breeding season is in full swing right now. It may require more in-cage time until it passes.
Analyze the situation and observe everything that she is telling you before she feels the need to bite. Yelling at her isn't going to change a thing, except that she might start yelling back. Remember, behavior has function.
Lots if good reading on this site and lots of topics in the behavior forum...read, read, read and read some more!!