If both parties agree, you can get divorced as and whenever. The divorce is completely seperate from the ancilliary relief (financial/who gets what)
I filed for divorce in Feb 02 (split in Jan 02)and was completely divorced in October of the same year. The financial side took another 8 months after this.
I take it that she is divorcing you but is now stalling at the decree nisi stage. You could threaten (via your solicitor) to begin seperate divorce proceedings and this may give her the jolt she needs.
It may be worth speaking to your wife yourself. Sometimes a couple can decide upon a course of action and then solicitors stir things up. This invariably leads to everything slowing down, emotions becoming turned upside down and the solicitor watching their fantastic earnings accumulate as the time ticks on.................