The property is a huge 6/4.5 duplex with an unfinished mother in law suite in the backyard.

Finding a property that pays you to live there, or with a mother-in-law suite and an ADU, will also come with a unicorn on it!

I don't know how to get her insurance info without letting her know that a lawsuit is coming.

If you are concerned about lawsuits, I would talk to a lawyer. 

But if you have followed the rules, keep your place safe, and have no real just cause for them to "go after" your personal property, is it common for frivolous lawsuits to move forward,  and has anyone (that you know of) been burned by not having an LLC because of this (lost it all)? 

Good practice...good lawsuit avoidance, great risk reduction tool, but not required.#2...in Texas and probably most places almost all properties are sold "as is".   

If you mess up on one thing and risk going through a lawsuit it can kill your cash flow or worse. - Would I be able to self manage?

The taxpayer can redeem at any time for the first three years, and can still redeem at any time afterwards up until the investor files a judicial foreclosure lawsuit and the judge grants the judicial foreclosure order. 

One of the key aspects of insurance is you also want the insurance company to defend the lawsuit for you. 

The "hottest" class action lawsuits against landlords are denial of housing to those with criminal convictions.