The daughter can dispute it, but whether she’s successful is another matter. The situation you describe–an elderly policyholder making a last-minute beneficiary change before death–is a common scenario leading to life insurance disputes. Usually in such cases, a former beneficiary questions whether the newly named beneficiary took advantage of the policyholder.
To challenge the policy change, the daughter needs legal advice. The life insurance company doesn’t have the authority to decide who’s the rightful beneficiary. Only the courts can make a finding, and the life insurance company will follow whatever the judge decides.
This won’t be an easy legal battle. Life insurance policies are considered legal contracts, and it’s very difficult to prove fraud, particularly when the new beneficiary was the policyholder’s wife. The daughter may feel the change was unfair and that her stepmother overstepped her bounds, but this still doesn’t constitute fraud.
Taking the case to court could also take a lot of time, energy and money. While in dispute, the court would put the life insurance payout in a trust, and the estate would stay open, with fees, taxes and penalties accruing. Many cases go instead to arbitration or mediation, in which the two parties negotiate an agreement instead of fighting it out in court and watching the life insurance payout dwindle away as legal fees accumulate.
Life insurance experts recommend policyholders review their policies regularly to keep them updated and make sure they have witnesses, including a professional financial adviser, when making any kind of change that could be controversial.
For more, see Can you dispute a life insurance beneficiary?