It is irresponsible and unethical but (by law) not illegal since nobody keeps up with how many times a female dog has litters or how often. Please note she had LESS PUPPIES in the second litter, and that is a common OUTCOME of breeding back to back litters - where the female cannot get a chance to REST and RECOVER.
All ETHICAL and responsible breeders let at LEAST one heat cycle pass, where she is NOT BRED, before breeding a female again. The more litters she has, and the more often she is bred (esp if back to back to back) the GREATER the likelihood of COMPLICATIONS, death of the mother and/or some puppies, and often, the smaller the number of pups in the litter produced and the LOWER THE BIRTH weights - making survival - LESS LIKELY.
Any vet can tell all of you that, if they can be bothered to take her in for a health exam & to ask questions before breeding again - but you can also GOOGLE this information.
Of course, truly reputable breeders do a series of health screening tests on the mother & father of any litter, LONG before breeding to make sure they are INDEED healthy - since Goldens have so many genetically passed along..... health problems.