Hmm.... could be multiple things, maybe a mood swing? (Though I don't know if it's that--) Maybe it's possible that they might feel left out a bit and or don't like the other friend? I think what Mawile said is best to do, it could be anything that could explain why they're acting that way to you. So while I have a few theories, it's best to try and ask them and get the answer out of them.

Description: -Sal