has anyone tried to or managed to marry Clea?  game keeps telling me her acceptance chance is impossible...maybe I have to lower her willpower?

Yes, you can marry her. Although that may have changed with the recent versions.

Max  out (or close to max) her happiness, corruption and affection. And get her wilpower to 20 or lower.

Getting her willpower below zero may also allow you to divorce her and possibly sell her in the slave markets.