May be give anthropic a try the answer is more correct than ChatGPT, indeed in every subsequent attempt the quality of ChatGPT both GPT-3.5 and GPT-4 deteriorated.

Here are the answers:

    ChatGPT:
      First response: 
        Mary is the sister of Susan and Susan has 7 brothers. Each of these 7 brothers has one sister, and that sister is Mary. So, Mary has 7 brothers, and she is also the sister of Susan. Therefore, Mary has a total of 8 sisters, including Susan.

     Second Response:
       Mary is the sister of Susan, so she has one sister. There is no need to consider the 7 brothers in this context as the question is asking specifically about how many sisters Mary has.

    GPT-4 Response:
       From the information provided, we can infer that Mary has one sister, Susan. The question specifically asks about how many sisters Mary has, and it doesn't mention any other siblings. Therefore, based on the given information, Mary has only one sister, Susan.

    Anthropic:

     Okay, let's break this down step-by-step:

      Susan has 7 brothers
      Each of Susan's 7 brothers has 1 sister
      So there are 7 sisters total (1 sister for each of the 7 brothers)
      The question asks how many sisters Mary has
      Mary is not mentioned anywhere else in the problem
      So there is no information provided to determine how many sisters Mary has

     Therefore, the question does not provide enough information to determine how many sisters Mary has. The number of sisters Susan's brothers have does not tell us anything about how many sisters someone unrelated named Mary has.