You might be pleasantly surprised and find that your little girl becomes less picky as she sees friends eating things she never would have eaten. Both my boys have become better eaters since starting school. Peer pressure isn't always bad...
Sarah x

We were on the free food program for a bit & since the kids pretty much *had* to eat what was given -- unless I knew for certain they didn't like it, then I would pack but that was only after they at least tried it once. Our school has 5 different choices (2 hots, 2 salads; sub sandwich) though & out of those, there is usually at least 1 thing they will eat.
Amazingly enough, they ate things that *I* won't eat!

I'm actually a picky eater though (and contrary to a quoted post -- I was actually a boring teenager as in the song "Goody Two Shoes" by Adam Ant comes to mind), so I liked the idea of the hot lunches so they could get to try foods that they would never be exposed to here.
For that matter my kids like ketchup & I don't, so a lot of the things they like if they can dip it in ketchup.
As for packing, as long as PB is allowed at your school & your child likes it. I have one who isn't allergic, just doesn't like PB&J sandwiches or much of any type of PB sandwich. I have another that doesn't like PB at all & a 3rd who loves it but had kids that have allergies in his class last year, so I just make him jelly sandwiches & he's OK with that.
My kids like summer sausage so we did sandwiches with that. We mostly did sandwiches though as my kids don't care for soup type things.
I do usually just ask them what they want. Fruit works well too if they aren't big sandwich eaters, etc... I know my kids love grapes so if I figured they were a little light on a main meal type thing, I would overpack the amount of grapes, etc... If they didn't eat them all that was fine but at least they would get full.