If I am getting sued for something that did not occur at my house but am getting blamed for it, what are my options?

A child I was babysitting for was in my care for the duration of the day, at 4:55 the mother picked the child up. The mother does not have a medical marijuana license, and has said to other neighbors in the neighborhood that she believes I smoke marijuana because she believes she has smelt it faintly in the morning during one drop off. After picking the child up at 4:55, she then started writing me around 6:15 asking if her child was acting strange that day, in response my answer was no. She insisted that since she picked him up from my care that he was limp, and lathargic, and not himself. She took him to the urgent care around 6:15 and it was discovered he had THC in his system. The mother is known to buy THC gummies from another person in our neighborhood that has a medical marijuana card, and she even disclosed this information to Department of Children and Families. The police and DCF came out to my house and did investigations, and I was not arrested, or found to be at fault.