Hi Shery, welcome to the forum.
You've posed a very tricky question that probably only the ECO can answer.
In principle the UK divorce decree absolute is not essential.
Here is the UKBA guidance:-
SET1.17 What if the divorce/dissolution process is not yet finalised?
An entry clearance should not be refused for this reason alone. The ECO would normally expect to see evidence that the divorce/dissolution proceedings are well under way.
While the divorce/dissolution may well come through within the six months Leave to Enter (LTE) period, thereby enabling the couple to marry, the ECO should be aware that divorce/dissolution proceedings may take longer than 6 months to resolve.
Should one of the partners still be waiting for a divorce/dissolution to come through at the end of the six-month LTE period, they may apply to the UK Border Agency for an extension of stay. Once married, the applicant may then apply for Leave to Remain (LTR) as a spouse.
The problem facing the ECO is just how long will it take before you can conclude the marriage. Fiance(e) visa is just 6 months.
Extensions to the 6 months ARE possible upon application.
I would have thought the ECO would need to see the decree nisi as a minimum plus a letter stating if there were any difficulties that might delay the granting of the absolute.
Sorry can't be of any more help.
But at least there is some positivity within the UKBA internal guidance.
Hope everything works out. Don't lose your hope.