Is it wrong to not speak to my mother inlaw?

shes 70 yrs old,her husband died this past yr,she tells so many lies that creates proplems in our family,shes constanltysaying my sister in law is trying to borrow money from her,my sister inlaw denies it, some of the things she tells people are so crazy,last yr she got got stealing from the salvation rm and got put on propation,(she had money)my hubby has quit talking to her and told me not to even try to get them back on seaking tems ,when we went over there to talk to her last week she jumped up and said shes neverlike me in 23 yrs,,ie always took her ever where shes needed to go,,store,doctor etc,,i told hubby she neds to get checked by the doc but hes done with her,,she wont listen to me so ive havnt spoke to her in a week,,im tired of all the drama and touble she creates but ive been the only one that helps her,,please no bashing,,im just confused and dont kow what to do,,she doesnt driveeither,i just want her to stop telling lies help,,thanks