[Chris38]

Spoiler for 45:

I don't think that Ruby is planing to kill herself, since this isn't a manga, where major characters die, and Ikeda probably realizes the fact that he might lose some popularity among his fans, if he made one of the main characters die...

So, I believe that Ruby's "prohibited magic" has some side effect, that will, most likely, make her unable to fight, till the Fairy Tail operation is over, and that will, change the tide of the battle, since someone from the group, would need to concentrate on protecting Ruby...