Texas Family Code Section 2.102 deals with Parental Consent for an Underage Applicant. The section makes it clear that parental consent is sufficient only when the child is 16 years of age or older but under the age of 18.
Based on your statement that the child is 15 years of age, parental consent alone is not sufficent in Texas. It would require a cout order granting the child permission to marry.
It should be noted that, if exhusband attempts to approve the child's marriage, without proper authority, Section 2.102(g) makes it a Class A Misdemeanor. Section 2.102(f) makes it a third degree felony to misrepresent the child's age on a parental consent form.