It depends who the owner of the policy is. If the owner was the stepfather or his daughter, than he/she can do that. If your mother was the owner, than probably not. The owner is not always the person that purchases and pays for the policy. If there is a lot a stake, hire an attorney to notify the insurance company that you do not agree with the policy change.
If you'd like to discuss, please feel free to call. Jeff Gold Gold, Benes, LLP 1854 Bellmore Ave Bellmore, NY 11710 Telephone -516.512.6333 Email - Jgold@goldbenes.com
Mr. Gold is correct - the question is one of ownership of the policy, and possibly the validity of transfer of the ownership of the policy. The owner, however, would have the authority to change the beneficiary.
The above is general legal and business analysis. It is not "legal advice" but analysis, and different lawyers may analyse this matter differently, especially if there are additional facts not reflected in the question. I am not your attorney until retained by a written retainer agreement signed by both of us. I am only licensed in California. See also avvo.com terms and conditions item 9, incorporated as if it was reprinted here.
I agree with the other attorneys here. I just wanted to add that sometimes there is an argument that there was consideration for not revoking or changing designations. It is important to try to get to the bottom of the documents and see if there were promises made in writing between them.