First off, sorry to hear about the financial set back, we can totally relate. I love the name plate idea, the barrette ribbon idea and the decorated flip-flops. Paired with a home-made card or a colored picture for her friend, those are all lovely, thoughtful gifts for a best friend!!
I also like the idea from the poster about a coupon for something to do together in the future, since the girls are so close. How about a movie night in a couple of weeks, where she comes over and they watch a movie in pajamas, eat popcorn, bring her her favorite doll? Or a Girls-Day-In party where you paint their nails, do their hair, whatever. My daughter did something like that with her two best friends and it only cost a bottle of Mr. Bubble (they soaked their feet in plastic buckets) and nail polish, which I normally don't buy, but perhaps you already have on hand.
Janis recently posted a question about "Green Gifts" a couple days ago. If you can scroll back and see her posting, there were tons of inexpensive ideas.
Here is my posting from that question,
Can he select a couple of his books to give her? We have a Go-Green Book Brunch each year and parents/kids bring their used books to pass along to others, rather than have the books sit dusty on shelves or end up in landfills! Everyone leaves happy with a bag of "new" books for their family.
I love the potted plant idea from the first poster. A pot, bag of soil, packets of different seeds and maybe a little pair of gardening gloves!
You could make your own homemade Play-Doh. There are recipes on-line.
My kids love to put together homemade activity books. Do you have a printer and xerox (color helps, too)? We print off activity pages from on-line sites (word search, mazes, dot-to-dot), then add poems, sticker pages, recipes, jokes, homemade Mad-Libs, photographs of whoever the book is for, etc. We bind the pages (use hole-punch and yarn if you don't have a page-binder (Office Depot) . These are a huge hit for car trips or overnights.
Do you knit? Could you knit her a little purse? I don't knit very well at all, but I have made my kids bags using straight knitted rectangles folded over and sewn at a seam, then a knitted strap sewn on.
Good luck!