07/14/2011 at 04:00 PM EDT
is head-over-heels for her new little girl.
"Baby Harper is the most beautiful baby girl I have ever seen," the former Spice Girl, 37, who welcomed her first daughter
with husband David Beckham
on Sunday, Tweeted
four days later. "I have fallen in love all over again!"
And she's not the only one fawning over little Harper Seven Beckham
. The Beckham brood – boys Brooklyn, 12, Romeo, 8½, and Cruz, 6½ – are also spending quality time with the family's new addition.
"We all feel so blessed," added the mom of four, who announced she was expecting a girl
in March. "The boys love their baby sister so much."
Not that Beckham's excitement to meet baby Harper is anything new.
"She was saying, 'I just want her to get here and want to be holding her in my arms – not in my belly,'" a source told PEOPLE
. "She was so excited and really just ready for the baby."