i see javi not being able to stand being around someone who is constantly tearing themselves down, so i would imagine he would be right beside her, lending some encouragement along with some flattery. i'm sure he has tried to stay neutral throughout the whole casual relationship between them even though james is his best friend.
javi is a total sweetheart. he tries his best to be there for his friends as much as he possibly can, taking the description of being loyal to heart. he likes to be honest, but if the truth is bound to hurt someone's feelings, he doesn't see anything wrong with telling a little white lie or two, although he doesn't like to make a habit out of it.