It’s a children’s book (I think a chapter book) about a girl who is going to a birthday party (she may not be very well off?). The present she brings the birthday girl is her favorite book (?) or some book wrapped in newspaper, I think it’s the comics page. These girls go to multiple places during the birthday party – they start at a make-over/dress-up place (like Club Libby Lu, but I don’t know if it was named that), and all the other girls get cool outfits like fairies or rockers and protag gets pirate. She definitely is disappointed by this costume as I’m pretty sure she can’t afford to go otherwise and this was her only chance to go. Then they go to a restaurant and I think something bad happens there too. At some point they open presents and protag’s book is the only inexpensive and “uncool” gift. Finally the birthday party ends at a hotel where they are supposed to have a sleepover, I think the girls talk about playing a prank or something, but the protag calls her parents to come home early I think??? I don’t remember any conclusion to it but I remember all the details very vividly.
Lost Classics of Teen Lit: Name That Book! 