It might be helpful if you post photos on this Board. Sometime a project is unfinished because of an issue with it. I just quilted a quilt top my great-great aunt made that had been stored since the 1950’s. But she had made a mistake cutting out the triangles around the edge, which meant she left no seam allowance. I was able to power through and appreciate that done is better than perfect.
But if you are going to finish the quilt your Mom started, you want to make sure that your not making it more difficult for yourself than it needs to be. There are lots of hand quilters on this board, which is why a photo might help. Some questions a photo might answer: Is the top mostly flat? Is the basted sandwich mostly flat? Is the batting suitable for hand quilting?
I hope you can enjoy the process of finishing this precious gift.