It is "la voiture", therefore "elle" and "neuve" both are in the feminine form since they refer to it. You don't say "c'est.." because you refer to a specific vehicle, in which case you use "elle" instead of the impersonal "ce".
Here is the lesson on this: https://progress.lawlessfrench.com/revision/grammar/when-to-use-cest-or-il-est-elle-est-to-say-it-is
-- Chris (not a native speaker).
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