What should i do? advice?

I think your friend made sure she didn't invite Brianna because you were going to be at the breakfast. But I think she would get over it. Girls hold grudges but not for too long. You should ask Brianna for her phone number or ask if she has a facebook. To just add her on facebook might make her think you are stalking her unless you guys have a lot of the same friends, than that wouldn't seem weird...hopefully. But the best bet would be to ask for her number and if she has texting.