my problem with one tag question

Hello, everyone

I'm a newcomer here from Taiwan, and thank God for finding this place to solve my problems.

I've got a problem with one tag-question sentence.

Here it is: Mom said you were sick yesterday, __________?

If we want to make a tag question for it, which is the correct one, " didn't she" or "weren't you"?

I know that many grammar books tell us to make tag questions according to the main clause except for several certain situations,

and thus the answer to this question seems to be "didn't she."

However, what I'm thinking about is the real purpose of using tag questions.

As far as I know, the function of tag questions is to confirm a statement or guess.

And in my opinion,

what the speaker wants to make sure in that sentence we mentioned is more likely to be whether the person wes sick or not

instead of whether Mom mentioned about it or not.

Am I right?

Thus I'm so confused about this sentence, and hopefully somebody can solve my problem as soon as possible.

Thanks a lot!