First Boy/Girl party

  So Catie got this invite in the mail two days ago addressed to her...clearly written by a boy.  I though  "oh cool one of the boys sent her an invitation to the party that we are already planning on attending"...nope I"m wrong as usual.  I did not open it...because it was not my mail, but it was tempting.
  Catie burst in after school asking " is it here yet? is it here yet?"   She had already been informed of it's impending arrival.   She also was notified she was the only girl invited by the boy in her class.   He is a set of Triplets and his dad told them they could each invite three guests.  The Boy in Catie's class invited two boys and Catie.  The Girl invited three girls and the other Boy invited three boys...so Catie is the exception to the rule.
  Catie has been telling me for weeks she has a crush on this boy and he has a crush on her too...
They ride the same bus and have know each other for several years and love to play basketball together.  Catie's favorite sport.   So there was so real surprise that he invited her to his party...I am sure it's all very puppy dog and lady bug.  It so cute really.
   As the matter of fact when I was her age I was never invited to these kind of things...I was never the popular kid...so I am fearful if I don't let her go I will be sending the wrong message to her friends that we are overprotective...
Catie is a good kid and I know we can trust her,I just don't know the other parents so well.   I have only briefly met them and will have to talk to them before I am ok with this.   This is a big step for my little girl and I want to know she is going to be ok...She is only 9 and is so young.