Unfortunately, you don't supply sufficient information to give you a definitive answer. This is something of a complicated problem to solve without certain bits of information. You should really consult with a local attorney who is well-versed in civil litigation.
There could be statute of limitations issues, valuation issues and there is always the consideration of what the law firm (and/or Wal-Mart) is promising in exchange for the demand. These issues are the kinds of questions which an attorney could resolve with you and your daughter fairly quickly and (ideally) inexpensively. Many attorneys offer free or low-cost initial consultations, and such an initial consultation might give you sufficient information to make an informed decision on how to proceed.