The situation is serious but not as dire as it might feel right now, and understanding the legal framework helps clarify what she is actually facing.
Courts cannot technically violate probation solely for failure to pay fines and fees if the person genuinely lacked the financial means to pay. The Supreme Court has addressed this, and incarcerating someone purely because they could not afford to pay is constitutionally problematic. However, the distinction between cannot pay and chose not to pay is one that judges examine carefully, and three years of nonpayment on a $15,000 obligation after completing probation is a fact pattern that requires explanation.
The transfer to Collin County, where the original sentencing judge presides, is where the outcome gets determined. That judge has the authority to decide what happens next based on the full picture of her situation. The worst case is that she is ordered to serve whatever remains of her original suspended sentence. The best case, particularly if she can demonstrate that the nonpayment was a genuine financial hardship rather than willful avoidance, is that the judge sets up a payment plan, reinstates probation with modified terms, or finds another resolution short of incarceration.
The time between now and that Collin County appearance is the window that matters most. An attorney who can document her financial circumstances during those three years, demonstrate any good faith efforts toward payment, and make a compelling argument for an alternative to incarceration gives her the best possible outcome in front of that judge.
The bond in Dallas County is a positive sign that the court is not treating this as a high-flight-risk situation. Use the time before transfer constructively and get legal representation in place before she appears in Collin County.