mix somebody/something ↔ up phrasal verb 1 to make the mistake of thinking that someone or something is another person or thing SYN
confuse, muddle up with
I always mix him up with his brother. They look so much alike.
I think you might be mixing up Wetherall and Newton.
I must have got the times mixed up.
Ok, I have a 2 year old son, he knows who is his grandma & who is his grandpa clearly. However, he uses the vocabulary “grandma” & “grandpa” wrongly. That is when he calls his grandma “Grandpa” & calls his grandpa “Grandma”. Again, it is just that he uses the terms incorrectly not because he couldn’t distinguish them.
Is it right to say “You mixed grandma up with grandpa” in this situation?
But I think “mix somebody/something ↔ up” is about that people don’t distinguish who is who not because they use the terms wrongly.
You’re right, saying he mixed up the grandparents implies that the child can’t distinguish them. But if you put quotes around the words “Grandma” and “Grandpa,” then you’re clearly talking about the words, not the people.
You mixed “Grandma” up with “Grandpa.”
unambiguously communicates the proper meaning when written.
There’s no difference between the two versions when said aloud, so in that case the given sentence is correct, if ambiguous.