We have a book on stars that says Bellatrix is pronounced bell-LAY-trix. Properly in Latin, I believe it would be pronounced more like behl-lah-treex, but I have to say, I like how we've anglicized it. It has a certain flow to it. I love this name, and I was fascinated by Bellatrix Lestrange. I can't see the name Bellatrix for an honest person, though: I think it will always have a certain cunning feel to it.
https://en.m.wiktionary.org/wiki/bellatrix