Mother not rational, lying and filing lawsuit based on lies. How can we keep my mom from wrecking us financially with lawsuit based on lies?

We took my mom in to our home after she lived alone for 1year. In that time she became depressed, lived in disgusting conditions (sticky floors from spills never cleaned up, pooping her pants, not showering). After pooping her pants one time she went to clean pants in sink in the middle of the night (she fell asleep and left water running in the sink and flooded her house) we had to handle everything to get house fixed. In addition to this she fell 3x (that we are aware of). We took her into our home while repairs were done but my mom never moved back into her house. After living with my mom for a year it became unbearable (she would talk non stop, ask the same questions every single day (like asking if she could eat something, where the butter goes, let us know she is taking a shower and ask if it was ok to learve the fan on the bathroom on so the mirror didnt stay steamed up, and more). She fell multiple times in that first year at our house. She would become sick multiple times but resist going to the doctors saying it was just allergies (my whole family became sick many times from my moms "allergies"). The lack of privacy for everyone was unbearable for us all. As she lived with us and we showered her with love, made sure she made regular dr appts, started eating with us (if we did not cook for her she mostly didnt eat<when she did, she sometimes put bread WITH THE PAPER PLATE in our toaster oven and we had smoke alarms go off...obviously she was not safe to live alone). we never told her she had to move out (even when she tested positive for HEP C--it caused friction that my mom would wipe her nose and sneeze into her hands without using tissues...she would also cough constantly without using tissues or washing her hands--trying to protect my family but still care for my mom I gave her cough drops and tissues and asked her to use them as well as wash her hands. It was decided that if my mom wasn't going to move back into her house and she would continue to live with us. We could not afford to buy a house big enough to accommodate us all and give us all the privacy and space we desperately needed. My wife and I made a painful decision to sell our dream home to buy another big enough to accomodate us all with privacy. An agreement was made (which I stupidly didnt get in writting) that my mother would gift us the money from the sale of her house as a NON-REFUNDABLE gift; even if "gift" wasn't the word that was used between us, it was understood that the $ was non refundable, would be used to purchase the house, but not be returned to her nor would it be returned to any estate. My mom thought long and hard about it...discussed it with many people. Some were very unhappy (my brother and sister). Then to avoid even the appearance of evil we had my mother writed out the check to the mortgage copmpany (without which we could not have gotten a mortgage because of the debt-income assessment wouldn't allow it. The banker did not draft a gift letter because he said it was a joint account. No one could have forseen how my mom would act after the 911 call made for her benefit, but I do feel that does not excuse the banker from doing his due diligence to protect my wife and I from this very thing). We found one house that was large enough but needed alot of work. Wanting my mom to be safe and happy we bought it. At first my mom said she was satisfied if we could make some changes. The costs to make all the changes began to add up and my mother AFTER the house was purchased became more and move vocal about her dissatisfaction (what before could be fixed was no longer possible according to my mom). So we sold that house and paid all the costs associated with the sale of this house as well as the purchase of the next house. After calling 911 for my mom who was suffering from R.A. pain my mom became enraged (screaming, cursing, telling lies, and even slamming a door on my head) she refused to have contact with us but is suing us for failure to care.