SOLVED. YA adventure / possibly fantasy/ different bedrooms in apartment/ treehouse/ health nut father

[Holly]

I read this book in the mid 2000s, I am 25. Book about a girl, likely in Manhattan whos dad is a health nut ( vividly remember the mention of spirulina crackers), I believe dad is a psychiatrist, girl has different bedrooms in apartment with different themes from diff times in her life. One is treehouse, one is princess etc. goes on an adventure with a new friend.

what is this amazing book!!

[Holly]

It’s pish posh by Ellen potter !

[Capn]

Holly wrote: "It’s pish posh by Ellen potter !"

Pish Posh for trackable