the highlighted line in red seems weird to me....
I mean, just give her will do, and say 'Happy Birthday i hope you
like it' , you dont have to recite poems to her 
For cake, a small one will do
For musicbox, im not sure, perhaps someone will answer that
A cake + a small gift like bracelet.... i used to buy from perlini
silver too during sec sch days.. $15-$20
will definitely match your budget
and i might add another handmade birthday card for her
