Tango is a Border Collie/Toller ... and I definetly think your pup has Border Collie in her. I don't really think Sheltie or ACD but it'll be easier to tell once she's grown up.
I agree I also agree I also see Akita,St.Bernard. As soon as I saw her I thought border collie. She looks alot like Tango's brother Winter.
What ever she is she's adorable