Separated couple who own a home together. What rights do the parties have to enter?

As long as you and your wife are both owners on your deed, she has as much right to enter the home as you do. Changing the locks will not prevent her from breaking in, which she could do without any legal repercussions. But, if she is having a friend access the house using her key, changing the locks would prevent that from occurring. The friend would risk criminal charges if he/she broke into the house.

If you have filed a divorce complaint, you could file a petition with the court asking for exclusive possession of the house. If granted, that Order would allow you to change the locks and exclude her and anyone else to whom she has given a key. The fact that she has lived in TX for more than 6 months and appears not to intend to live in the house should be helpful in persuading a court that she should be excluded, except under certain circumstances to allow her to verify that you are maintaining the house in good condition. I suggest that you consult an attorney to review your options.