I would pronounce it, "hih-LEHR-ee-uh" or "hih-LAIR-ee-uh." (That's the same pronunciation written two different ways.)
My sister's name is
Hilary so I may be biased. But
Hilaria is fresh and appealing to me.
I knew a woman with this name who spelled it HaLarear. She pronounced it the same way you do. The spelling is all the more surprising because I'm in the U.S. where we take our "r's" seriously. And yet, HaLarear was said just like
Hilaria. She said she had no idea why it was like that; it was a family name.