"Ik draag geen bril, maar zij wel."
Translation:I do not wear glasses, but she does.
Because the helping verbs need to match.
I AM not wearing glasses but she IS; I DO not wear glasses but she DOES.
By looking at the verb:
- Zij eet rijst = She is eating rice
- Zij eten rijst = They are eating rice
Edit: Note that in this sentence, "zij" could be either 'she' or 'they', because there is no verb in the second part of the sentence.