Oh dear, steer clear. She is toxic. She could be telling the truth about her son, in which case she may be having a hard time with it. Or, she could be lying, in which case she will eventually be found out and fired. All I can say is for you to let the bosses do their job and try to tough it out while all of this goes on.
I agree with everything Lori said. Let your bosses deal with it. Getting involved in this mess won't help you.