Actually I think it is safe for me to assume her normal appeals have been exhausted. If this is not true, please let me know and I'll update my answer.
At this point her options are obviously limited. However, you seem to be indicating that you have discovered new evidence that you think would have substantially altered the outcome of the trial. In that situation the proper petition to file is a Writ of Error Coram Nobis. This is a petition to set aside a verdict and grant a new trial where new evidence has come to light that would substantially impact the outcome of the case. These writs are used to prevent "manifest injustice" that can be created by keeping out newly discovered evidence that would exonerate a defendant (such as newly discovered DNA).
Texas courts have held for some time that a Writ of Habeas Corpus is the only recognized action to challenge a standing judgment. Therefore your attorney may have to either 1) file the writ in federal court or 2) file the writ as a habeas writ and make the factual allegations and manifest injustice argument. The practical effect has combined the titles to these writs into one, but the arguments are distinctly different. Your attorney will be able to guide you.
I must point out that this is a long shot. However, you will want to discuss this with her attorney along with numerous other potential procedural challenges she may file under the Writ of Habeas Corpus route.
Please reply if I can help further.
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Edited by JD on 3/6/2010 at 12:17 AM EST