Any time you violate probation, you are exposed to the remaining time on the maximum sentence for the underlying offense, which in this case sounds like grand theft. So, it would be possible for her to get the maximum for that, assuming it is five years, minus all time already spent in jail and already on probation or house arrest.
While that's the maximum, it is also possible she gets less and that depends on the judge, the recommendation of the prosecutor, and the facts as presented and mitigated by a defense attorney. Deny the affidavit and speak to a defense attorney before going forward. Good luck.
For a third degree felony, the max is 5 years prison. But be aware that sentencing depends on the judge and some judges are more punitive than others. She first needs to consult with an attorney that practices locally to get a better sense of her sentencing options. Scoresheet guidelines are also very important, so be sure to check that they are accurate. Once you hire an attorney, they will also examine any defenses she may have as to the positive test. Sometimes the tests are done improperly, or the results are flawed. Before she admits to violating her probation, she needs to examine whether or not she could prevail at a VOP evidentiary hearing.