Being Sued to appear before County Court

Hi, I am new here, and found this site. Excuse me if this isn't the right forum to post. :)

I'm trying to help my Mother in law. She just received a citation letter about a CC debts and is being sued. We're in Texas. She has to file "a written answer with the clerk who issues this citation by 10am on the Monday next following the expiration...". I am trying to do my research on how do i go about in this. This is my first time dealing with this. So any help or answer will be very much appreciated.

The Plaintiff in this is Equable Ascent Financial LLC. I have read through some post in this forum and this letter has a "Request for Admission" with 17 bullets. This is kinda similar to the one post I read here. One of the bullet says that the "Plaintiff made demand on Defendant for the payment of the outstanding balances due at that time" and my MIL told me she has never received such letter or any "settlement letters" from them. This is the first time she had heard of them and it is through this Citation letter. So, this statement from ESF is a lie.

She mentioned it's her Chase CC, and the last payment made (she think) was in 2008. Amount owed is about 3k.

As you can tell, I have no clue on how to figure out how to even start. I did tell her the first step is to go to the court and have the written answer and don't run away. She has no money to pay for attorney or any legal fees.

Do I tell her to write a DV to ESF or is it too late? What is my first step in this?
Please shoot me any questions that will help you in helping me dispute this case :D

Thanks in advance!