My 21 mnth is refusing the bottle due to molar teething i guess. Will she drink bottle back again?

Most toddlers do go back to the bottle once the teething discomfort settles, so it is usually a temporary phase rather than a permanent refusal. My girl did the same around that age, and once her molars came through properly she was back to her usual feeding routine. It might help to try a softer teat or offer the bottle when she is calm and drowsy, as some kids find it easier then. That said, at 21 months she is at an age where transitioning to a sippy cup or straw cup is also quite manageable if the bottle refusal stretches longer, so either way you have options lah.