How should fiddlers prep for jam class or camp?

The advertised requirement is “able to change smoothly between simple chords”. A fiddle doesn’t exactly chord, but a fiddler needs to be able to follow simple chord progressions, and be aware when the song is on a G, or on a D, etc. That allows for playing of correct backup notes for either bowing or “chopping”, and if she ventures a lead, using licks that are most easily categorized by what chord(s) they go with.

Important: For bluegrass jamming, it is not really sufficient for a person to know only how to play tunes and lead lines. This is where bluegrass and other kinds of music differ: All instruments are expected to play backup, for which there is no printed music available. You just have to watch (the guitar player’s left hand) and listen for chord changes, and play something appropriate, even if it’s a single note for each chord. So it’s important for fiddlers to know what the different notes are that go into a G, C, or D chord, and to get to them quickly and smoothly. It’s actually ok if they just hit the root notes, G, C, and D, and that is a basic workable place to start.

Aside from that, a new fiddler would benefit a lot from being able to find melodies by ear. It’s fine to start slowly and haltingly, but after a while it should come more quickly and accurately, and that’s a great place to be when the camp gets going, so that she can try faking a melody in a jam now and then. To start that, suggest some favorite songs that she could hum, and the likely key (G or A works for many). If you can sing the song slowly and play guitar while she tries, that could really help get her going. Watch out, though, husbands and wives don’t always match up so well as pickers when one is ahead of the other one. Just being encouraging is the best thing, especially if she’s sensitive to criticism.