Do not mix "voidable contract" with "contract breach", as they are somewhat contradictory and won't jel well together.
There was only one contract that was ever standing b/w BDW and MINTO, that's the APS signed by both parties without the floor plan. Yes, the version BDW signed had the floor plan, but that sketch was not accepted by MINTO and they removed it at the time of signing and executing the APS, therefore the floor plan was never a part of the legally binding contract. As far as the official APS was concerned, MINTO did not breach anything (notwithstanding the incorrect reference to the model).
If normal practices were followed, the signed APS wouldn't become binding immediately until BDW had a chance to review it again (in 5 business days). If these were all true, then one can't really accuse MINTO for unilaterally changing or "forging" the contract. MINTO's fault was that they did not explicitly inform or explain to BDW about the alternation they made, and because of this, BDW mistakenly entered into a contract that didn't reflect her true intent. Again, this warrants the contract to be voidable.
