Depends. Sometimes things are correct when setup but regulations change and the plans are not adjusted. If they were incorrect from the beginning then you may have a case. Contact a legal malpractice attorney in your state to review all the elements in your case.
You may also want to contact the original attorney to see if he has a suggestion as to how to correct the situation or possibly reimburse you for damages.
It is not uncommon for the VA to 'get it wrong'. I'd not jump to the malpractice conclusion. Annuities come in different flavors and varieties and the appeals process often results in V.A. decisions on benefits being reversed. I'd speak with Jim Swain at firstname.lastname@example.org in the Atlanta area or call an attorney who is a member of the AVAPP.org Good Luck!
I suggest you obtain a critical review and opinion from an attorney experienced in estate planning and VA benefits. You might consider visiting wealthcounsel.com and/or estateplanning.com to find a lawyer who can review the facts from a legal standpoint, and perhaps come up with a way to handle the situation without litigation.
This response is not to be considered legal advice, it is for information only. You should always consult with an attorney to obtain legal advice.
Get an experienced, VA accredited elder law attorney to review the facts. VA eligibility planning for the Improved Pension benefit gets complicated and its easy for a VA clerk to misconstrue or misread the governing statutes and regulations. More often than not, I have found its VA has gotten it wrong. There is an appeal process that is in place; that appeal process is there to protect your mother's interests.