First and foremost, every time you breed a bitch, regardless of color, there's a very real chance that she will die, and that some or all of the puppies will, as well. Before any other considerations, you need to be sure that you are prepared to take that risk. As well, you need to be sure you are financially prepared for any eventually - meaning you should have at least $3,000 set aside for an emergency c-section, medical care, what have you, as well as time off work banked because if you do lose the bitch but have puppies, they will need round-the-clock care for the first several weeks.
Onto issues specific to breeding white Boxers - yes, they have a higher chance of deafness themselves, and the foremost expert in canine deafness has stated that any puppies they produce - white or colored - will also have a higher chance of deafness. Blindness is not linked to the extreme piebald gene, which is responsible for white in Boxers, though it is linked to the merle gene which causes white in other breeds like Collies and some Great Danes. The AKC will register white Boxers and their progeny (if other AKC rules apply); the American Boxer Club Code of Ethics prohibits the breeding, full registration, or sale (for more than a specific limited amount) of white Boxers.
The fact that your bitch is not on a limited registration and spay/neuter contract calls into question the responsibility of her breeder; if they ignored the Code of Ethics as far as white Boxers go, did they also ignore the important health testing necessary, or the evaluation of structure and temperament? Will you, if you breed your bitch, be producing puppies with the best chance of a long, healthy life, or will you be perpetuating or perhaps bringing out some serious issues which are lurking in the pedigree? If you don't know the genetic health of the Boxers behind your bitch, you're breeding blind - and in this breed, where some of the most common health issues often mean the dog drops dead at 2-3 years of age without any prior signs that something is wrong, breeding blind is the last thing you want to do.
Also, you should know that "we want one just like her" is one of the top reasons irresponsible breeders give to breed. Remember, she is only contributing 50% to the puppies; the sire will have a say, as well, and as has been mentioned, you may end up with something completely different from your girl. Also, I'd wager that the traits you love about her are very typical of the Boxer breed in general - you could find those traits in another well-bred puppy without risking your bitch.