Finding it difficult to get the lighting right on white flowers. I've tried different times of day...and I just can't seem to capture the luminosity without the blowout.
I think you've done good with the whites and the pastel purple of the center portion of this is also very nice. I like this shot over the other one because of the angle and the fact you can see the dotted underside of the petals. I agree that it is a little soft but this can be overcome to some degree in pp. The problem with clearing up the flower is the graininess you'll get as a side effect but you can help that by processing the flower separately from the bg. If you get graininess on the flower when you do this then use the blur tool and blur on the petals while leaving the edges of the petals alone.
Hope you don't mind but here's an edit I did to show you what I mean. This is just a quickie off of your posted image but if you did it to the original it would probably work much better.
This is pretty good work as far as whites go, and lovely flower, but it seems to soft on the edges... It may be intentional, but it isn't working for me.