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I am very sorry to hear about your daughter's situation.
The visa is still valid, although it will only be until (a) the divorce is finalized, and (b) USCIS finds out about this. Since most divorces - even if uncontested - can take months to process, the visa is still technically valid. NOTE that if he contacts USCIS and tells them of the pending divorce, she may be waylaid upon entering US on the visa, but eventually should be let through. But again, the visa will be cancelled if he goes through with the divorce, because the visa is conditional for 2 years and is dependent on the marriage, and only then can she get a permanent greencard status.
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