i also believe she had started to hand quilt it. i can't imagine she would have pinned it (which is, itself, a method of basting) AND put it into a hoop with the intent of adding thread basting.
on a basic design such as that, larger quilting stitches look quite appropriate and will be lovely. she was most likely planning to bury that little knot and tail later on.
i would continue the quilting as she started.
she loved you dearly, i'm sure. she would want you to enjoy the process of finishing her last project. she wouldn't want you to worry or take on more than your current skill can handle.