My fiance signed what she was told was a 2 year lease for a new car and found out later it was for four years

People who sign contracts are deemed, in the law, to have read and understood them, else millions of people would clog the courts with claims that they did not read or understand the contractst they agreed to.  Moreover, to claim fraud, a person must reasonably have relied on the misrepresentations made to them.  If the 4 year term of the lease was in the contract itself, it was not, as a matter of law, reasonable for your fiance to rely on any representation to the contrary.  Therefore I don't think your fiance has any legal basis for getting out of the contract, but the dealership may be willing to compromise somewhat to avoid any hassles with the better business bureau or bad publicity from your fiance's complaint.