We would write it as follows:
And you tell her “you are crazy,” don’t you?

The semicolons would not be appropriate unless your sentence contains commas as in the following example:
“First, you find the present; second, you open the present; third, you look at what it is; and last, you say thank you.”
See Rule 2 of Semicolons, our post First vs. Firstly: When to Use Each One, and the our Confusing Words and Homonyms page.

We see no reason for a semicolon. You may find our complete list of Rules for Semicolons helpful.

As we mention in Rule 4 of Colons, “A colon instead of a semicolon may be used between independent clauses when the second sentence explains, illustrates, paraphrases, or expands on the first sentence.” Therefore, occasionally it is a matter of writer’s discretion as to the use of the semicolon vs. the colon. Our example of such a case in Rule 4 is He got what he worked for: he really earned that promotion.

While we would favor a semicolon over a colon in your “flamingo” sentence, a colon would not be incorrect.

As Rule 1 states, “A semicolon can be used in place of a period to separate two sentences where the conjunction has been left out.” The sentence in Pop Quiz question 1 could correctly be written as either
Let’s go dancing; afterward we can get dessert. OR Let’s go dancing, and afterward we can get dessert. Sentence 1B, Let’s go dancing, afterward we can get dessert is incorrect because it is a run-on sentence.

Similarly, use of semicolons in your example results in a run-on sentence. Periods are required. Your example should be written as follows:
I’m still confused about it. Do you use it instead of a comma, because on the pop quiz it looks like it. Did I use the semicolon right?
Please see our Rules for Semicolons and Rules of Commas for more information.

Like a flamingo, this sentence structure has two legs; each leg of the sentence must be able to stand on its own.

Having read your chapter on the semicolon, I’ve noted that semicolons and colons are not interchangeable, but one of the quiz answers (on the semicolon) states that both A) & B) are acceptable, so perhaps either may be used here?

My own sense is that it needs a colon, not a semicolon, following the Fowler rule that the 2nd clause “pays” what is “invoiced” in the 1st clause?

Thanks so much for a really helpful site.