Translation:She is a celebrity in China.
To add, there are a few times when 在 follows the verb, usually with certain specific verbs like 住. More here: https://www.chineseboost.com/grammar/zai4-after-the-verb/
Although a dictionary may list 是 as "to be," that is just the infinitive (base) form. When 是 is used in a sentence like this, it translates to "is"—the conjugated (modified for context) form of "to be."
Using "to be" here implies that her purpose for being in China is to be a celebrity, like she specifically went to China to become famous. While that may be true, the sentence given only states that she is a celebrity in China, so the extra implication of using "to be" instead of "is" would make your translation inaccurate.
Hope this helps!