I saw some GIFs as though it had been turned into a meme at some point, but I even went back to the screenplay and it just isn't there.

http://www.springfieldspringfield.co.uk/movie_script.php?movie=matilda

I watched it on bluray recently and I'm sure that line is still in the movie. I'm gonna take another check soon.

In the movie I've watched, there are two scenes where the mother leaves to play bingo. In the first scene she's talking about "soup" and "heating it up if you get hungry", in the second scene it is about "fish fingers in the microwave".

First Scene

Voice-over
By the time she was two, Matilda had learned what most people learn in their early thirties:  how to take care of herself.
As time went by, she developed a sense of style.
Every morning, Matilda's older brother Michael went to school.

Zinnia: "Come on, get out of here. Make money."

Voice-over
Her father went to work, selling used cars for unfair prices. And her mother took off to play bingo.

Zinnia: "Soup's on the stove. Heat it up if you get hungry."

Voice-over
Matilda was left alone. That was how she liked it.

(Then you see Matilda take a pan with a can of Campbell soup in it and throw it away. She then makes pancakes).

Second Scene

Voice-over
By the time she was four, Matilda had read every magazine in the house. One night, she got up her courage and asked her father for something she desperately wanted.

Harry: "A book? What do you want a book for?"
Matilda: "To read."
Harry: "To read?! Why would you want to read, when you got the television set sitting right in front of you?"
Harry: "There's nothing you can get from a book that you can't get from a television faster."
Michael: "Get out of the way."

Voice-over
Matilda already knew that she was somewhat different from her family. She saw that whatever she needed in this world, she'd have to get herself.

Harry: "Goodbye."
Zinnia: "Ciao. There's fish fingers in the microwave."

Voice-over
The next morning, after her parents left, Matilda set off in search of a book.

(Then we see Matilda looking through the telephone directory and she walks ten blocks to the library).

I hope this answers the question. Unless you have another version.

Ah Wonder2Wonder, that must be it. Thank you, but do you know what I even said to my sister finish the line "There's fish fingers in the microwave" and she finished "heat them up if you get hungry!" I guess it's just one of those things people commonly misremember.

@John1990 said:

Ah Wonder2Wonder, that must be it. Thank you, but do you know what I even said to my sister finish the line "There's fish fingers in the microwave" and she finished "heat them up if you get hungry!" I guess it's just one of those things people commonly misremember.

It's an easy mistake, the scenes are right next to each other.