Realistically - say you WERE able to obtain a monetary judgment against her for fraud. How do you ever expect to collect it? Sometimes the fight just isn't worth it. It doesn't sound like this is an individual you'd ever be able to collect a dime from on a judgment. People get judgments all the time and are not able to collect.
If you're talking about a criminal action, that would be brought by the DA and with an overburdened system, chances are they wouldn't bother to file against her.
As for the disestablishment of paternity and releasing your partner from the CS obligation - because of public policy reasons, the courts are typically highly unwilling to do this, especially after 14 / 15 years have passed.
How was paternity established originally?