It depends on a lot of factors. Drawings can be considered "child pornogrpahy" under the right set of facts and in the right place.
For purposes of this question I am assuming that the flash drive is located in Texas.
There are a number of Texas laws that could apply but the one that fits the best is Texas Penal Code 43.26. You can see it at http://www.statutes.legis.state.tx.us/Docs/PE/htm/PE.43.htm
Under those definitions even drawings can be considered as child pornogrpahy. Plus, if it is being sent over the internet, there are other state and federal charges that can apply as well.
Yes, the wife could potentially be charged. When you read the definition of "possess" it clearly covers this situation.
The wife could likely get herself out of trouble by hiring an attorney, turning the material over to them, and getting the attorney to get it to the police. If she wants to turn the husband in then she could definitely get immunity if she lets the lawyer handle it.
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