Help for my underweight 13 yr old

Meat! Nah, I'm just kidding. I just wanted to be the FIRST to say it because inevitably, at least 100 more are going to! I've been enjoying my english muffin, peanut butter and apple lunches. You can stack them all together or whatever. Do they have access to microwaves? If so, I have a couple of veggie pasta recipes that freeze/fridge and reheat well I could give you - and they're totally easy to make! I can give you my whole meat-less list I made before Lent if you want. There are several frozen meals - Lean Cuisine, Michalina's, etc. - that are veggie friendly. When I was in jr high, my bff and I would eat 12-20 packs of wheat crackers and a coke for lunch just about everyday. Tho, I wasn't raily either. Just saying that it might not be anything to worry about, just a phase.
Katie doesn't eat a lot of meat either and takes her lunch MOST of the time, and I usually send her a big variety of things because she has to wait 20-30 mins after school for me to get her and she likes to have a snack. Our usual variety is: pizza lunchables (tho they can be pricey), yogurt (especially GoGurt), pretzels, goldfish/whales, peanutbutter/cheese crackers, fruit, string cheese, fiber one brownies, cereal/granola bars, fruit snacks/rollups/by the foot, rice crispy treats. She usually has at least 5 of these things (plus a water bottle) in her lunch box everyday. Of course, sometimes she shares/trades and usually there is something left over, but that way I know she's not gonna open that bag and think "I'm not in the mood for THIS." There will be something that will look good. (I pack my own lunch and snacks with the same thought in mind. LOL)
And, what if you pack the "components" for a sandwich separately and she can build it herself? Would she do that? Idk, since I'm not cool enough for middle school. LOL!

I wouldn't stress too much. If she's eating fine at home, one meal of crap isn't great but she'll be fine.

I have a tiny little 13 year old too and she's the exact same way. I encourage her to eat fruits and veggies and her school *does* have a salad bar, so I know she'll eat some of that. But........I just do my best to make sure she's getting good food at home. I know that with what she gets at home, she's getting the nutrients she needs.

And, also, her dad and I were both small kids too. I'm not super worried about that.........she's healthy and otherwise ok,

How about investing in a lunch box with a sort of cooler/ice pack in it? I got a great one at Target for $10--keeps sandwiches (and other foods like cottage cheese, cut raw vegetables, string cheese, fruit) from getting funky after sitting at room temperature. :flowerforyou: Plus, the lunch box is so cute, I can't help but want to pack my lunch (and I'm in college--it's miraculous).

What about things like sunflower seeds, cheese or peanut butter and crackers, apple and caramel dip, what about the flavored rice cakes? Girls at that age are pretty self conscious as they are still figuring out who they are and are often affected by what their peers think.

My kids like to snack on things like cashews, peanuts, or peanut butter roll ups (whole wheat tortillas with peanut butter in them). Sometimes I put peanut butter and nutella in them. Also, maybe something like Ensure drinks? The chocolate ones are pretty good. However, if she's eating properly two out of three times a day, then it isn't a total wash....

I agree with your daughters sandwich dislike. When I made sandwiches I would take all the ingredients in mini plastic dishes.Then, made the sandwiches just before i ate them.

Alternatively, how about something like Asian rice balls (onigiri/ kimbap). I'm sure you can find info online.

Some wonderful things you can prepare for her (depending on her wants) are bean/rice dishes. Most schools will let a student warm up meals and those are high protein items that can help her gain some weight. Make sure that whatever you prepare are high fiber, high protein ( like nuts and trail mix) but HEALTHY. Don't send your kid to school with a candy bar or sugary drink. Take her to the store and let her pick out her own nuts that she likes and there is a lot of bite sized candy (like m&ms) and make trail mix. It can be healthy as long as you watch how much candy is being put into the mix. As for the meals, if she likes things like spaghetti or lasagna those are things that can be made meat free. Also, have you tried to prepare any tofu meals for her? Other snack options include nutella (which has a chocolate taste) and peanut butter.