I believe that your chances of having this overturned are VERY minute. Depending on the amount involved, it might be worth trying to challenge it. "She" might decide to settle, as opposed to going to trial on this, since it is a pure windfall for her. This would be a very tough case, however, and you would need a very skilled probate litigator to bring it with any hope of prevailing.
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As Attorney Frederick mentioned, this is a challenge. It is probably worth some effort depending on the amount at issue. Contact a local probate attorney for a fact specific analysis.
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