Her bond order will have any conditions expressly stated in said order. Unless the judge made not leaving the state a condition of bond, she may leave the state provided she returns for court. Except in serious cases, or cases where there is a reason to believe the defendant will flee, remaining in the jurisdiction (or state) is not typically a condition of bond.
Consult the bond order for specifics in your (her) case.
Unless specifically noted on the bond, there is no rule against leaving the state while out on bond. The issue that does come up is notice. The court will send court dates to the address she provided to the jail when she bonded out. If she isn't at that address, doesn't get the notice and doesn't show up for court, an arrest warrant will be issued for her failure to appear. The law does not care that she didn't actually know about it. All that must be done is to send it to the address she supplied. So she had better make sure that she gets her mail or has someone she trusts getting it for her. Also, she will want to be sure to have reliable transportation back from Texas. Getting to court is her responsibility and failure to appear is a good way to end up back in jail until the case is over.