SOLVED. Book about an out of shape middle school girl and her homeless friend who is searching for her "dream home" [s]

[Rachel]

This book must have come out by at least the early 2000's, probably before that though. The main character is an out of shape middle school aged girl with little to no friends. She is obsessed with marine life and the ocean in general. A new girl in the same grade as her moves into town, and begins attending school with the main character. The new girl is skinny, athletic, a good climber, and homeless. She lives in a van with her younger brother (who she has to share clothing with because there's not enough to go around) and her mother and father. She easily climbs the rope in gym class that the main character has always had trouble climbing and has never succeeded in doing. The homeless girl at some point in the book finds a house key on the side of the road with her bare foot, which she believes will unlock the door to her "dream home", and all she has to do is find the house and it will be hers (obviously this never happens, though at some point in the book she does find an old abandoned decrepit house in the woods, and is disappointed when the key does not unlock the door like she hoped it would). The main character (the out of shape girl, sorry at this point I can't think how else to describe her with what little information I've given you) at some point in the book is given permission by her parents to redecorate her room by herself. Her mother is very angry when she sees that the girl has painted the walls a very dak, almost black, navy blue (like the deep ocean), and has taped up pictures of fish and marine life all over the walls, to try to make her room look like an underwater sanctuary.
I think at the beginning of the book the main character had a friend, who was also out of shape. But then her "friend" had doctor's orders to lose weight, and when she did her acne cleared up and she became "pretty", and therefore got in with the "popular crowd" and was embarrassed of her old friend (the main character) and so didn't want to associate with her anymore. (This part could be from a different book and I'm just mixing them up, because I think there was a part like that in the book Fat Chance by Leslea Newman, but I'm pretty sure it's from the book I'm trying to remember the title of).
I can't remember much more than that. Other than before school starts all the students have to wait in the gymnasium on the bleachers for class to start, and the out of shape main character doesn't have any friends to sit with and is embarrassed by this, because everyone else sits with their friends.
Please help!
-R.R.C.

[Rachel]

That would explain the chapter entitled "MOVE...THAT...BUS!".... :P

[Rachel]

I knew nobody would know what I was talking about! Ha

[Rachel]

More information: it was fiction, and I believe it was juvenile, though it possibly could have been YA. I probably read it ten or so years ago. I am almost positive it was a standalone book and not a series book, but I can't be sure about that. If it was a series, I never knew it. Help!

[Kris]

Book mentioned by Rachel in message #1 -- Fat Chance by Lesléa Newman.

[Rachel]

Fat Chance was a good book too; and the title was clearly easier for me to remember! Ha-ha.

[Sarah]

The Fastest Friend In The West was published quite a bit before 2000, but seems to fit.

Here's the review:
Grove puts a human face on the issue of the homeless and dispossessed, making one family's plight bitterly real. Lori isn't sure what to make of Vern, with her tight T-shirt and scabby, dirty knees; but she can empathize with Vern's dreams of planetary travel and sky-walking above the troubled earth. After all, pudgy Lori--who privately thinks of herself as Lorelei the mermaid--has just painted her bedroom to look as much as possible like the bottom of the sea. When Vern leaves school, Lori realizes that she has lost a friend; and when the two meet again, Lori discovers that Vein's space-walking fantasies help her forget that Veto and her family have been living in a station wagon for the last 15 months. Vern and Lori know each other so fleetingly that some readers may wonder how they manage to become so firmly involved in each other's worlds, while their story--first "Lorelei's" account, then Vern's--is occasionally redundant. But the portrait of Vein's family is both realistic and sympathetic; a bad economy and hard luck have put these people on the road, and their vulnerability is frightening and poignant. Generous and moving. (Kirkus Reviews, April 15, 1990)

[Rachel]

Yes, that was it! I read it in the 2000's, but I had no idea when it was originally published. As soon as I read the title though I knew that was it. Wow, awesome. I can't believe I finally found it! Thanks so much. Case closed!