I don't live in Texas, but as far as I can tell from Nolo, it's legal to rent your own property in every state. The person you talked to may have thought that you were listing someone else's property, or she may have just been confused or malicious. It is possible that she flagged you as spam. I have suspected that in the past when I've turned someone down as a prospective tenant. But there is no way to know for sure.
I like Craigslist because I can do prescreening by email.
If you are new to renting property, be sure to read up on how to screen tenants. LOTS of the people who respond to my ads have terrible credit or no job or a criminal record. You really need to be careful.