What it means
Revocation is the cancelling of a will so that it no longer operates. A will can usually be revoked by making a new will that expressly revokes earlier ones, by physically destroying the will with the intention of revoking it, or by a formal written declaration. In most Australian jurisdictions, marriage automatically revokes an earlier will (unless it was made in contemplation of that marriage), and divorce typically revokes gifts to the former spouse. The exact rules vary by state and territory.
How it's used
By signing a new will, she achieved revocation of her earlier 2010 will, which no longer had any effect.