The best thing to do here is to call the Texas State Board of Realtors and to ask.  Referral fees or fee split arrangements are common with certain types of businesses but generally within the same profession.  Attorneys can refer cases to other attorneys and real estate agents often split their fees.  So the real estate agent may in fact be correct: it may be illegal for her to pay a referral fee or enter in to a split fee arrangement with anyone other than a licensed real estate broker.  The Texas Board of Realtors may have the information on their website as well but for members only so inquiry is probably necessary.