Wow, I have to agree with everyone else in that what this LA quilter did isn't right. This is a very large quilt and it sounds like her frame wasn't large enought to do the whole width of the quilt. But as others have said, she needed to unpin and and turn it so she could do the other sides and probably more than once in order to reach all the corners. I can't believe she charged you more than quoted and didn't even finish the quilt! She should have also known what her rack limitations were before taking on the job, it makes me think she hasn't been LAing for very long to know what could and could not fit on her rack. I can't believe she came highly recommended to you. I too, think you should go back to her but it sounds like you have reconciled yourself to not dealing with her (or him) any more. I would still go back and give her one more opportunity to make it right. If she does not you need to warn others about her bad business practices.
I have to ask... Are you happy with what she did do?
As far as completing it yourself, at least the center is done and FMQ the remaining borders will be easier to do because you don't have to cram too much of the quilt in the throat of your machine. However, it takes a lot of practice to get even stitches and smooth movements FMQ on any machine. I would be inclined to handquilt the remainder of it. At least you have a ton more control handquilting and should be able to more easily replicate the quilting motifs she used on the LA, even though the stitching will look different from what she has done. You should also mention something to the people who highly recommended this quilter so they know she (or he) isn't all they thought she was.