My advice for when you want to explain a scene change without narration is the awkward Sarah solution.
First, you have a Sarah.
Then you have her suggest going somewhere more private to discuss something.
This is where awkward Sarah is awkward, and makes what is roughly the equivalent of small talk to establish that information while working up the nerve to actually ask what's wrong.
And then you can proceed with someone being sad for reasons they themselves find incredibly confusing! HOORAY!