I've never encountered “labia” pronounced to rhyme with “crabbier”. I’ve only ever heard it said the way you’re used to.

(Citation: When Club 18-30 ran their oh-so-wearily-provocative “Beaver Espaňa” campaign in the early 1990s, the best—in fact pretty much the only—example my flatmates and I could be bothered to come up with in response was “Saudi A-Labia”.)