Please answer! will a collie/shepherd mix puppy grow up to be a BIG dog?!?

my family wants to adopt 2 dogs, a small one & a big one...i found this adorable 4 month old collie/shepherd mix puppy up for adoption. she was a puppy mill survivor and her description says she's the sweetest dog ever! i reallly want to consider her, but my family is already looking at another big dog...and we can't have 2 big dogs :( she looks pretty bug for a 4 month old puppy...does that mean she will be big as an adult? if you look up on google images a pic of a 4 month old german shepherd she is about the size of them...i just reaally feel like this dog was meant for me<3 sooo basically my question is, do you expect a collie/shepherd mix to be a big dog (about as big as a golden retriever, bigger or smaller?) and would they shed alot? thanks!!!