It's too much, especially when you have other, fairly obvious, angel-themed names in the same story. Also, it sounds too much like "hello" and if any character ever says "Hello, Halo" it's going to sound ridiculous.
How about Tiara?
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin