What a wonderful legacy! Your grandmother will live on and be refreshed in you mind every time you look at the quilt. How you must have loved this special lady!
I definitely think she had started to quilt it by hand. The stitches, while rather large, are very even, and I know that I was told that while the size is important, it is how even they are that is most important. If you continue as your grandmother started you will have a beautiful heirloom with a rustic, charming look.