Here is the item again:
After Deidre saw the tiny balance on her ATM receipt,
(A) she
realized, (B)
that her meals for the next week would consist of cheap
food, (C)
such as peanut butter sandwiches and instant soup.
You correctly realized that the comma after realized was wrong. That her meals for the next week would consist ... is a subordinate clause. When you attach a subordinate clause to the end of a main clause, you usually need no punctuation.
To fix this problem, you chose to do this:
After Deidre saw the tiny balance on her ATM receipt, she
realized that her meals for the next week
would consist of cheap food, such as peanut butter sandwiches and instant
soup.
You have correctly employed Punctuation Rule 1:
Main clause + Ø + subordinate clause.
Excellent choice!