In an Indiana Small Claims Court, the regular rules of evidence that would normally present many problems in getting the court to consider the text messages do not apply. Instead, all the Court is interested in is if it thinks that the text messages are true copies of the correspondence and agreements between everyone.
This means a couple of things. First, the Judge will want to know if the text and other messages were really sent or if someone will dispute that they actually sent something (if this happens, you will need some proof that would show that they did send it and not someone who just happened to grab the phone and text something for sake of texting someone). The next issue for the Judge is are the texts and other message actually what was sent between everyone (ie, no one changed them, cut anything out, etc...). The other issue is getting everything in front of the Judge - in many counties in Indiana (and other states), Court Security will not let anyone other than an attorney get into the Courtroom with a cell phone.
The other thing that would help is if you could produce copies of the checks (if there were checks) or other proof that she had been paying and something suggesting that the payments were for rent and not anything else. This information would corroborate the information in the texts and what not. Good luck!
While I appreciate the opportunity to answer your question, my thoughts and impressions of your case may change given more information. Typically, I would give advice following a face-to-face meeting where we could both ask questions of each other about your situation. Therefore, my answer is intended to be general guidance and not legal advise for you to rely on in your particular situation. Moreover, my response to you is not intended to establish an attorney-client relationship. If you would like to hire me as an attorney, you must contact my office and we must enter into an agreement for me to represent you.