I just need to know if im crazy?

hi well me and my girlfriend work at the same place. we both work at a theme park at one of the roller coasters. at work there is this one girl who is 11 years old and comes to the park everyday by herself. she brings everyone at work cupcakes on a day to day basis and her mother has never been seen. one day she came to my job with invitations to her birthday party. i immediately knew it was a horrible idea to go and my girlfriend felt the same way. two other people when to the party came back and told my girlfriend about it and said it was really fancy and was just her family there. my girlfriend now insist that if the little girl invites us to another party we should go. i strongly disagree with this because i do not feel as if it is our place to be at her party where we know nothing about this little girl except for that she is 11 and comes to the park everyday. i just want to know if im crazy and should be more accepting to go or am i doing the logical thing by not allowing her to go.