What do I need to do if she doesn't leave and I need to evict her from my own home?
Contrary to popular belief, there is a rent contract/lease.
She is protected by state law.
No property transactions can take place without a lease, contract, or statutory protections anywhere in the USA.
This protection/requirement stems from English common law and the infamous or famous "statute of frauds".
Our Texas legislature has created a statute to allow for month to month tenants at law, rather than by lease (should the parties so choose).
How Eviction Process Works: A Serial Guide And Tenant Ouster For Landlords
You can offer her MONEY to leave voluntarily.
If you choose that option, make sure you draft a contract indicating you will give her $XXX to leave on SOME DATE CERTAIN, take all of her junk, and the money will be paid when she and all her JUNK have been removed from YOUR home.
You can pay her at police or sheriff station, make sure you add that to the contract.
Protect yourself, and never allow anyone to live in your home.
You live in a home, not a hostel.
Protect your home.
Your other option is the obvious one, a formal eviction.
This explains eviction in Seguin County:
Justice of the Peace, Precinct 3
http://www.co.guadalupe.tx.us/jp4/pdfs/evictions/how-to_eviction.pdf
A JP Court:
Justice of the Peace, Precinct 4
You must choose the correct JP Court, if that applies, fir the place and precinct where the property is located.
Good luck.