Is "My drawing is gooder than yours" correct?

Why

Tanya has applied the standard short-adjective rule correctly in principle — "good" is a short word, exactly the kind that usually just adds "-er". "Good" happens to be one of a small handful of irregular adjectives that change into a completely different word for comparison, the same way "go" turns into "went" rather than "goed": good becomes better becomes best, not gooder or goodest. There's no spelling trick that predicts "better" from "good" — it comes from an older form of English and simply has to be learned as its own word, exactly like the irregular plurals and irregular past tenses met elsewhere. Test: say "gooder" out loud in a sentence and notice how unfamiliar it sounds, compared to how automatic "better" feels — that gap is the sign of an irregular form you've already absorbed correctly through everyday listening. Her friend is right: "good" becomes "better" and "best", one of English's irregular comparisons, not "gooder".