A good friend loaned me the money to purchase a Mobile Home, paid for with a cashiers check. a week later, he died and now his estranged wife is claiming fraud and trying to stop the transaction, is this possible for her to do this?
It depends, cashiers checks can have stops placed on them just like a regular check. If the husband used her funds to buy the cashier's check she may be successful. Without more information it is hard to say.
Contact a commercial law attorney in your area. If he used her cash, but otherwise had funds to borrow you, and she causes a breakdown in that arrangement, you may have recourse against his estate?