So here's maybe the honest approach.

Let Shaina know that you haven't been entirely happy, and that seeing
your friends at that party made you feel happy in a way that you
haven't for a long time.  You need to see your friends more; this
isn't negotiable.  We should go on lots of adventures this summer, and
I want them to be part of it.

As for what were the thoughts I wanted to run past Moriah...

What the hell should I talk to Devin about?

  Yeah, that's a good one.