If you are not a licensed attorney in the relevent state, I would expect the attorney for the other side to disqualify you before the proceedings begin. It does not matter that you are working "pro bono". Your post states that you are a consumer.
It sounds as if what will occur is a debtor's examination to determine if she has any assets that can be used to satisfy the debt/court judgment.
The time to have raised the issue of who owns the debt, whether it was barred by a SOL, etc., was when she was first sued, not now. The judgment ilikely was granted by default quite some time ago. Unless you can prove faulty service and get the jdugment vacated, your client is stuck with that aspect of it. From what you have described, your client was aware of the law suit and court summons and blew it off.
If your client has an income and lives in a state that permits wage garnishments, then she is at risk of receiving one unless she is low income as defined in Federal statute. She also is vulnerable to a bank levy, assuming she does have a bank account. TX does not permit wage garnishments, but if she has money in a bank account, she may want to close it. She should cash her paychecks at one of those check cashing places. The creditor probably is going to have a difficult time proving she has tip income in any significant amount.
Your client probably has the option of discharging this debt in bankruptcy.
If she chose to ignore a court order to appear for a prior debtor's examination, then she should have been prepared to suffer the consequences. Court orders are not suggestions. Blowing that one off was a "bad move" on her part. However, judges are not eager to fill jails with debtors who probably could have filed for bankruptcy, if they had only been smart enough to realize it.
I suggest that she appear. If she has limited income and no assets, there probably is not much that this debtor's examination will do for this creditor.
However, judgments often are valid for many years, sometimes as long as ten or fifteen and in many states are renewable for another ten years or so. Her circumstances could change and the judgment could come back to bite her in the rear end as an incovenient time.
She still might want to file for bankruptcy. Depends upon how much she owes, whether she has other bad debts, etc.