Maruko has been told that she can't have the food she wants, and replies:
????. To the extent of dreaming of a day, some day, when I can eat (it), Maruko's ??? is.
I can't find a dictionary definition for 勝手 that makes sense here. The best fit seems to be "circumstances" i.e.
"My (Maruko's) circumstances are such that I dream of a day when I can eat it.",
If my translation is correct then it sounds very dramatic/formal in English. What nuance is this sentence structure adding over the more simple:
I'd also be grateful if you could tell me what いいじゃん別に means.