I've done it both ways. I've made the wholecloth quilts with oodles and oodles of gorgeous close, fine quilting (and in-depth abundant trapunto on 2 of them). They turned out very well. This is my true quilting passion!
But my brother likes quilts made more like a comforter. So I seamed the fabric to queen size, and layered it with a highest-loft poly batting (very thick) and then just did an overall large open meander on the top. This simply held it together without a lot of quilting to tack it down and firm it up too much. He loved it. Just what he wanted.
Either way is good and pretty. Just depends upon what your mom likes. Wholecloths are a ton of work, and lovely. The comforters are easy and fast, and a different look.
Hope this helps. Good luck!