If she actually held her self out as being licensed in Texas, and is not, that is unauthorized practice of the law and a violation of professional ethics. If, on the other hand, she merely is an attorney licensed in another jurisdiction and is representing you ex-boss' interests that may not run afoul of ethical requirements. Contact the Texas bar and have them answer your inquiry based on your particular facts and the local rules, requirements and prohibitions.
I agree with my colleagues. Contact the Bar. Keep in mind that if it turns out she is not an attorney while holding herself out to be one, that is a separate issue from whether or not she is harassing you and whether you have a claim against her for that.