it would be a peeniss situation once more except the love involved would be different obvs

but if this for some reason was unable then katniss would die for Rue x

It's hard to say. Katniss wanted to stay alive for Prim, but Rue really cared for Katniss....so maybe this? Or, I'm thinking, another berries situation.

I have an answer.... BERRIES!!!

obvs

This is what i'd hope would happen.

I think they will do this since they both don't like killing people.

I think it was because rue had cared for katniss and katniss gave food to rue that they formed an alliance and if rue had survived well, they wanted the other to live and would have killed theirself so their friend could live.
sorry for the long explanation :(

Probably.

probably the same she did with peeta

But I think they might have still done the berry thing

I don't think the berries trick would work in this scenario - people in the Capitol would be more invested in a romantic relationship than a friendship/pseudo-sisterly relationship, and also the 2 would hardly see each other in future because of belonging to different Districts, so again people would care less. I think Katniss would be the one sacrificing herself because Rue would just remind her too much of Prim, and possibly Rue wouldn't predict what Katniss was about to do in time to prevent her.