Homophobic Friend (knows I am gay) is in my brothers class!

If you aren't ready for other people to find out yet, then that could be a tricky situation. If you trust your brother, you could try sharing with him in advance. If you confide in him, he could help you to keep your secret until you are ready to share, and could help to serve as a buffer in his class in case this homophobe tries to start drama.

You could also try and send your friend a message, perhaps an e-mail or text message, appealing to your former relationship and asking for her to respect your discretion. just because she reacted in a homophobic way doesn't necessarily mean that she will try to hurt you.

 

Does she even know your brother? There's a chance that even though they're in the same class they'll never talk or become friends, so don't worry too much. Address problems as they come your way, because there's no point in stressing about something that hasn't happened and may not happen.

 

Well, this isn't the most practical advice by a long shot, but if you're quite convinced that there's no way to prevent being outed, maybe it would be easier to think of how you can deal with the situation if it happens. Given I don't know anything of use, I can't really think of how you would do so.