I had a very dear friend die and I did leave condolences on the funeral home's questbook. I really just knew her and not anyone else. We emailed and visited several times, knew each other about 6 yrs. She lived about 7-8 hours away. I would have felt very out of place.
I sent her Daughter and family a card with a personal note and her grown Granddaughter a personal card too.
Not every funeral is close by.