We've tried email, phone, text and even certified mail.

As a direct mail specialist I'm likely a bit prejudiced however considering all the agony inflicted by unwanted texts and phone calls these days, it's likely that your message stands a better chance to be seen/heard via direct mail.

In the mean time, if I understand their motivation and develop a unique angle, maybe I can get this at the right price. 

I'm a realtor in New Braunfels and am going to text a few of my local lender contacts and ask them!

or should I try to find out the sellers' motivation first? 

So if your motivation is to create complementary companies that can increase your profit then adding a PM company can be a great idea.

If you have texts saying they are going to sign it, and you delivered it some judges/courts will consider that a lease even though it isn't signed as well. 

It doesn't sound like she's motivated or ready to move out quite yet.

Six months ago, I was introduced to Brandon Turner and the Bigger Pockets podcast and it has transformed my motivations, goals, and really my life.

This was well thought out and slightly motivational.