Hi
A person who makes a will or changes a will must be of sound mind. The same applies for signing a power of attorney.
Some relevant questions when establishing capacity are:
1) Was your mother aware of and did she appreciate the significance of making the will?
2) Was your mother aware of the character, extent and value of her estate?
3) Was your mother aware of those who might reasonably be thought to have claims upon her bounty, and the basis for and nature of those claims?
4) Did she have the ability to evaluate and discriminate between the respective strengths of those claims?
If your mother did not have capacity the revocation of her POA may be invalid. Her new will, if she signed one, may also be invalid.
The contents of a will are confidential and that is why her lawyer will not give you any information.
You may have to take the matter to the Victorian Civil and Administrative Tribunal if the POA was revoked during a period of incapacity.
Regards
AV