Anonymous wrote:Everyone will ask her if she was born in October. It's an ugly name. Don't do something because it's trendy. You may think it's cute for a baby but this baby will grow up to be a 14 yr old screaming "I hate you" while wearing inappropriate clothes one day.

Um, 14 year olds who behave like that - and that's a lot of them - are going to do that no matter what you name them.
Opal's a very pretty name, OP. Doesn't sound any more childish than other names and less so than names I've seen like Minnie and Daisy and Jimmy (all actual names I have seen that are not nicknames but the person's given name). It will grow with her.