Rest assured, it's something that very few, if any, would actually notice
and they don't make a cosplay look bad. You are going to be fine!
Most likely people are just going to eye your attire and your efforts, not what is in your mouth! Braces afterall, are a regular occurance in the daily life of us human folk. It is also on behalf of your oral health afterall, and any normal person is going to understand that.
Really, I highly doubt you will get a reaction like "Oh neat that person has a really coo- OMFG SHE HAS BRACES.*CARDIAC ARREST*